Mistakes in the Harry Potter books

"As obsessive fans will tell you, I do slip up! Several classrooms move floors mysteriously between books and these are the least serious continuity errors! Most of the fansites will point you in the direction of my mistakes. But the essentials remain consistent from book to book because the story has been plotted for a long time and it is clear in my mind."

— J. K. Rowling on the errors within the franchise

Below is a list of mistakes that occur in the Harry Potter book series, such as plot holes and typos. Some of these mistakes were fixed in later editions of the same book.

Harry Potter and the Philosopher's Stone

Cover

• The art for the cover of the original UK edition depicts Harry at Platform Nine and Three-Quarters wearing a Gryffindor scarf, however, Harry hasn't been sorted yet. It is possible, however, that the illustration is of Harry returning to Little Whinging at the end of the school term (although given the look of surprise on Harry's face, this is unlikely as his expression would be more appropriate to seeing the train for the first time).
• The cover art of the original UK edition depicts another train beside the Hogwarts Express.
• The 15th Anniversary US cover by Kazu Kibuishi depicts Hagrid and Harry with only four fingers on their right hand.

Chapter 1: The Boy Who Lived

• The beginning of the story takes place on a "dull, grey Tuesday." But in 1981, 1 November was on a Sunday.
• The muggle news reports an unusually large number of owls awake and flying around in the daytime. However, no mention is made that the owls are carrying packages or letters, which is the only reason so many of them would be out and about during daylight, and for that matter, would make for a much stranger (and therefore newsworthy) sighting by muggle standards than just the fact that the owls are awake during the day.
• It is very unclear how much time goes by between certain events on 31 October and 1 November. Sirius arrived on the scene at Godric's Hollow the night James and Lily died, and Hagrid arrived there a short while later. When Hagrid picks up Harry from Godric's Hollow early in the morning "right before the Muggles started swarmin' around" he borrows Sirius' motorbike. However, Hagrid arrives on the motorbike late to Privet Drive when it is "nearly midnight" the next day, having not spoken to Dumbledore since he went to go pick Harry up. As the chapter depicts a whole day between when James and Lily died and when Hagrid arrives at Privet Drive, Hagrid and Harry are missing, or unaccounted for, for nearly 24 hours.
• It is unknown why Professor McGonagall was staying next to the Dursleys' home all day, instead of being at Hogwarts, tending to her duties as transfiguration teacher and head of Gryffindor House. It is highly unlikely that she was stationed there on Dumbledore's orders, as Dumbledore was surprised to see her there. It is also equally unlikely that she was there to see Harry be delivered to the Dursleys, as she was appalled when Dumbledore announced his intention to do that. The only thing she knew (as she heard this from Hagrid) was that Dumbledore was planning on coming here, but she has no reason to keep tabs on Dumbledore, especially at the expense of her duties at Hogwarts.
• Dumbledore says that he passed through several parties to get to Little Whinging, even though he apparently got there by Apparition, a direct form of transport, judging from his sudden appearance next to Minerva McGonagall. He could have apparated several times to go to many parties – possibly in order to lose anyone (such as Death Eaters) who might have been following him. It is also possible he walked or flew most of the way, and only decided to Apparate a very short distance to Privet Drive, though what motive he would have for this is unknown.
• In the Bloomsbury edition, on page 17, Hagrid says "I'll be takin' Sirius his bike back"; yet, in Harry Potter and the Prisoner of Azkaban, Sirius told Hagrid to keep the bike because he didn't need it anymore. It is, of course, possible that Hagrid intended to give the bike back in spite of his friend's protests, feeling Sirius may not have meant it. Still, in later editions of this book, the problem was fixed by having Hagrid say "I'd best get this bike away" instead.

Chapter 2: The Vanishing Glass

• Piers Polkiss is described as "a scrawny boy with a face like a rat," but in another part of the book Dudley's gang is described as all being "big and stupid" with Dudley being the biggest and stupidest.
• The trip to the zoo is said to take place on a Saturday, but Dudley's eleventh birthday (23 June, 1991) was actually on a Sunday.
• The boa constrictor at the Zoo supposedly winked at Harry during their conversation. As snakes don't have eyelids in real life, it is impossible for them to wink. The snake may have instead contracted his facial muscles around his eyes to appear to wink, though the possibility of even this is debatable. It is also possible, if unlikely, that snakes in the Harry Potter universe are slightly different from their real world counterparts, which would go along with their apparent higher intelligence.

Chapter 3: The Letters from No One

• Harry's 11th birthday (31 July, 1991) was said to be on a Tuesday. But in 1991 in the real world, that date was a Wednesday.
• On page 31, the sentence "Harry could see Uncle Vernon's shiny black shoes pacing up and down the kitchen" begins with a speech mark, even though the line is not being spoken by anyone. It is amended in later editions.

Chapter 5: Diagon Alley

• On Harry's Hogwarts list of school supplies, "1 Wand" is listed twice, as both the first and last item on the list. This mistake was fixed in later editions of the book. The list of school supplies also doesn't include potion ingredients, although Harry later buys them. In later editions of the book this has been corrected.
• Harry buys the book One Thousand Magical Herbs and Fungi, but later, he looks up dittany in "One Hundred Magical Herbs and Fungi". This error was, however, amended in later editions.
• The air in the tunnels of the Gringotts vaults is described as getting colder when you go deeper into the earth. However, in theory, it should get hotter as you go deeper as once you get below a level where the temperature depends heavily on the weather at the surface, the geothermal gradient takes over and it gets hotter as you go deeper. Of course, there may be enchantments in place to account for this discrepancy.
• When Harry returns from Diagon Alley to Little Whinging, he takes a train from Paddington Station. However, Little Whinging is in Surrey, south of London, so he should have travelled from Victoria or Waterloo; trains from Paddington head to the west.
• Despite Garrick Ollivander's claims that the original Ollivander arrived to Great Britain with the Romans, this individual started his wand-making business in 382 B.C. but the Roman conquest of Britain (Britannia) only began effectively in A.D. 43, under Emperor Claudius. An earlier attempt was made in 55-54 B.C. by Julius Caesar, as an adjunct of his Gallic campaign. Prior to then, the Romans had only sporadic contact with Britain, to the point where, up until 124 B.C., many Romans did not believe the land actually existed.

Chapter 6: The Journey from Platform Nine and Three-Quarters

• Aunt Petunia is described as looking as surprised as the other Dursleys about Harry needing to board at Platform Nine and Three-Quarters, yet according to Harry Potter and the Deathly Hallows, she had been there at least once. Although, she may have been pretending to be startled in order to distance herself from the magical world.
• Mrs Weasley asks her children which platform the train departs. However she should perfectly know this, since she departed seven times from the same platform. However, it is possible she only asks so her children remember.
• On page 79, the closing quotation mark is missing right after Hermione tells Harry about the books he is in. This mistake was fixed in later editions of the book.

Chapter 7: The Sorting Hat

• While being sorted into houses, Harry looks up at the Sorting Hat's stool, and there are only three people left to be sorted. Professor McGonagall then calls out the names of four more students. This error only occurred in the US edition and was rectified in later editions – in the UK edition Dean Thomas's name is omitted.
• During the Sorting ceremony, Sally-Anne Perks is sorted before Harry but in Harry Potter and the Order of the Phoenix, when everyone in fifth year are being called in alphabetical order to take their practical O.W.L.s, Parvati Patil is called before Harry. It should actually have been Sally-Anne Perks, but because many students were pulled out of the school that year, it is possible that Sally-Anne was cut out.
• When Harry first meets Nicholas de Mimsy-Porpington, the ghost says how he has not eaten in nearly 400 years. Yet he had, at the time, already been dead for 99 years longer than that. This was fixed in later editions of the book.
• It was stated in a previous chapter that Harry's birthday, July 31st, was on a Tuesday (regardless of what day it actually fell on in 1991), which would mean that September 1st was on a Saturday. The next day would have been a Sunday, yet classes began.

Chapter 9: The Midnight Duel

• Fred tells Harry that the Gryffindor Quidditch team hadn't won a championship "since Charlie left". Charlie attended Hogwarts from 1984-1991, and so had only just graduated as Harry arrived – Harry filled the seeker vacancy left by Charlie. It is a strange way to put it since no time had really passed since Charlie left, though Fred is still telling the truth as they hadn't won since 1986 which is when Charlie attended. It is possible Charlie, while still at school, had left the Quidditch team a few years before actually leaving Hogwarts.

Chapter 10: Hallowe'en

• During the Hallowe'en feast, when the troll is let in, Professor Dumbledore sends the students to their dormitories. But the troll is said to be in the dungeons, and that is also where the Slytherin dormitories are, meaning that Dumbledore has put them directly in harm's way by sending them there. The logical move would be for every student to stay in the Great Hall, do a roll call, and send teachers to go and look for missing students.

Chapter 11: Quidditch

• The narrator says that, if Gryffindor won the first Quidditch match, they would pull into second place for the House Cup. However, in Prisoner of Azkaban, the Hogwarts Quidditch tournament appears to have its own cup, independent of the House Cup.

Chapter 14: Norbert the Norwegian Ridgeback

• The night Charlie's letter shows up at Hogwarts is said to be Wednesday at midnight. However, earlier in the book it is mentioned that Astronomy classes take place every Wednesday at midnight which means that they are presumably skipping class, and the other students should not be asleep. This error was corrected to Saturday in later editions of the book.
• Curiously, McGonagall takes fifty Points from Harry, Neville, and Hermione for wandering around the halls at night, but she only takes twenty from Draco Malfoy for committing the same offence. Earlier in the book, she takes only five Points from Hermione for her allegedly going on a suicide mission.

Chapter 16: Through the Trapdoor

• During the match against the giant chess set, Ron says "Well, Harry, you take the place of that bishop, and Hermione, you go next to him instead of that castle". Except the castle is next to the knight, not the bishop. It is possible though that when Ron said "next to him" he didn't mean immediately next to, only in the general area of where Harry was located.
• Also in the match, Harry was acting as the bishop. His last move was to move three spaces to the left. However, in real chess bishops can only move diagonally. However, it could also mean that Harry simply moved 3 spaces left diagonally, and wasn't written properly.
• At the beginning of the same match, Ron is the knight in the giant chess set. It later says that he had to "move ahead one" so that the Queen could take him, opening the path for Harry to checkmate the king, and win the match. If he were a knight, he would only be able to move either ahead one, and sideways two, or ahead two, and sideways one. It is possible, however, that "one" was meant as one move, rather than one space.
• When Harry and Hermione drink the two potions to get them through Snape's task, there is only one bottle to get them through the black fire and only one bottle to get them through the purple fire. The smallest bottle holds the potion for the black fire, and it only contains enough for one person. If this is so, then it is unknown how Quirrell got to the Mirror of Erised in the first place.
  • Although, it's possible that the task just reappears again, just like the chess set was intact and Harry, Ron and Hermione had to play the game again.
  • It is also possible that Quirrell had only taken a sip of the potion himself, therefore only leaving enough for one more person.

Chapter 17: The Man with Two Faces

• Dumbledore says that his and Hermione's owls crossed in mid-air, however a few pages later Hermione says to Harry that she ran into Dumbledore on the way to the Owlery to send him the owl.
  • It is also possible that Dumbledore is not omniscient, as he admits himself. He is limited to the knowledge allowed by his own subjective perspective, and when Harry informed him of Hermione's intentions to send an owl he merely admitted that he hadn't received it. His reason for not having received it may have been wrong, but he didn't know she hadn't sent it. In English we say something "must have" happened in some way even if we aren't actually certain if that is in fact the way in which the thing happened.
• Dumbledore explains that only a person who wanted to find the stone, but not use it, would be able to get it. However, by that logic, Quirrell should have been able to get the stone without any problem, as he did not want to use the stone himself, only present it to Voldemort.
• If nobody could acquire the stone if they wanted to use it, then it is unclear how Nicholas Flamel was supposed to get it in order to make more elixir of life. Perhaps he had already decided that he was ready to die and had no desire to have the stone anymore, but then, why didn't he and Dumbledore just destroy the stone as soon as it was retrieved from Gringotts?
• It is unknown why Dumbledore and/or Flamel could not have used the Fidelius Charm to hide the stone and/or its whereabouts.

Harry Potter and the Chamber of Secrets

Cover

• The UK version of the cover illustration of Harry, Ron, and Hedwig in the flying Ford Anglia incorrectly depicts Hedwig as a barn owl rather than a snowy owl.
• On the front cover of the Spanish edition, Harry is holding the sword and looking at the Basilisk, but looking into a Basilisk's eye's is fatal, so, technically, Harry should be dead on the Spanish front cover. However with Fawkes having clawed out the Basilisk's eyes, Harry would be able to look on without fear of death.

Chapter 2: Dobby's Warning

• Petunia should have been aware that underage wizards and witches are not allowed to use magic outside of school, since the rule was written in 1875, well before Lily's time at Hogwarts. However, it could have been that Lily had simply forgotten to mention this to her.

Chapter 3: The Burrow

• After Harry, Ron, Fred, and George arrive at the Burrow, Mrs Weasley shouts at Fred first. Then she says, "and you two" glaring at Ron and Fred, but it should say George since she has already yelled at Fred. This error was corrected in later editions of the book.
• In the US edition of the audiobook read by Jim Dale, Ginny's eyes are stated as being bright green but in the printed US first edition, and the UK version of the audiobook read by Stephen Fry, they are said to be bright brown, which agrees with the description in Harry Potter and the Deathly Hallows of Molly's eyes being the exact same shade of brown as Ginny's.

Chapter 4: At Flourish and Blotts

• The Hogwarts' equipment list mentions the Lockhart book "Wanderings with Werewolves", but later, Lockhart refers to the book as "Weekend with a Werewolf". This error was fixed in later editions of the same book. 

Chapter 5: The Whomping Willow

• When Harry and Ron arrive at Hogwarts in the flying Ford Anglia, a scene which takes place on 1 September, 1992, they are told that they had been seen by Muggles in various locations, including the "Post Office Tower". But due to a change of ownership, the tower has actually been called the BT Tower since 1984. Also, the building is about a mile southwest of King's Cross, so to pass it, Harry and Ron would have had to be going in an entirely different direction to be following the Hogwarts Express.

Chapter 8: The Deathday Party

• Harry, Ron and Hermione go to Nearly Headless Nick's 500th deathday party. However, in the first book at the start of term feast he says he has not eaten for nearly 400 years, which would imply that this is how long he has been dead.
  • In later printings of the first book, Nick's comment is changed from "nearly 400 years" to "nearly 500 years".)

Chapter 9: The Writing on the Wall

• Hermione says that Moaning Myrtle haunts the bathroom on the first floor. However, when Harry sees the writing on the wall outside her bathroom, he is on the second floor.
• It remains unknown how Moaning Myrtle never notices Ginny visiting her bathroom, or the pipe door opening, or the Basilisk coming through her bathroom.
• Percy's name is once misspelled as Perry after he catches Harry, Ron and Hermione leaving Myrtle's bathroom.

Chapter 11: The Duelling Club

• When Harry speaks Parseltongue to the snake during his duel with Draco, everyone hears him hissing. Therefore, when Harry hears the Basilisk speaking in the walls, Ron and Hermione should hear hissing, yet they claim to hear nothing. A possible explanation for this could be that the Basilisk is hissing very quietly, so Ron and Hermione can barely hear it, but Harry can make out the words as he hears them in English.

Chapter 13: The Very Secret Diary

• When Harry is viewing the memory from Tom Riddle's diary, Tom Riddle says to Hagrid at one point, "The dead girl's parents will be here tomorrow." It is stated elsewhere in the book that Myrtle is Muggle-born. Muggles cannot enter Hogwarts. However, it is possible that an exception was made for them (the Muggle-Repelling Charm could be lifted a day or two, for this reason), or it could be that Tom simply assumed that Myrtle's parents were wizards.
• Valentine's Day in the book is depicted as a typical school day, albeit one where the cupid dressed dwarves are interrupting classes. February 14, 1993 was a Sunday, meaning there should have been no classes to interrupt.

Chapter 14: Cornelius Fudge

• When Harry is at the Quidditch pitch, reflecting with relief that there will be no one in the castle to become victims of the monster of Slytherin, Professor McGonagall shows up to say that the monster has struck again, and that everyone should return to their dormitories, presumably to keep them safe. However, the students would have been far safer to remain at the pitch while the professors checked the castle again.

Chapter 15: Aragog

• When Harry tells Ron to be quiet or the 'something big' will hear them, Ron responds, "Hear *me*? It's already heard. Fang!" However the sentence should probably be "It's already heard Fang!" as it is read in the audiobooks. It is amended in later editions.

Chapter 16: The Chamber of Secrets

• It is stated that the Basilisk was able to move through the castle's pipes, but it remains unknown how something as large as the Basilisk would be able to fit through the plumbing.
  • Based on the fact that Harry, Ron and Lockhart are able to move through the plumbing to get to the Chamber later on, it may be that the pipes for Hogwarts are simply that large, or may change shape depending on their load, just as the staircases can move.

• It is unclear how Fawkes spoke Parseltongue to enter the Chamber of Secrets to intercede Harry, nor how Ron could have been strong enough to help him get past the rubble caused by Lockhart's spell.

Chapter 18: Dobby's Reward

• On page 283 of some copies of both the US paperback and hardback editions, the word "professor" is misspelled as "professorr".
• Dumbledore tells Harry that Lord Voldemort is the last remaining ancestor of Salazar Slytherin. This is meant to say that Lord Voldemort is the last remaining descendant of Salazar Slytherin.
  • This error was fixed in later editions of the book.
• Dumbledore concedes that nobody will ever be able to prove that Lucius Malfoy slipped Tom Riddle's diary to Ginny before the start of term, let alone did so with the intention of opening the Chamber of Secrets; thus, Lucius could not be prosecuted. At the time Dumbledore says this, this is true. However, only a few minutes later, they suddenly have a witness they could have used against Malfoy: The newly freed Dobby! Bear in mind that, in Order of the Phoenix, Dumbledore offers to summon Dobby to give evidence in Harry's defence, and the Minister decided to accept Harry's version of events without needing the evidence. So clearly, house elves are not considered incompetent witnesses by the Wizengamot.

Harry Potter and the Prisoner of Azkaban

Cover

Full Scholastic (US) cover and back cover art

Bloomsbury (UK) cover

• On the US version of the cover, the front art is the night that Harry and Hermione save Sirius and Buckbeak. However, on the back side of the cover (Lupin appears as a werewolf), the moon is a crescent, but it should be a full moon.
• The cover of the Scholastic edition and British Bloomsbury edition both depict Harry and Hermione riding Buckbeak. Harry's legs are shown to be in front of Buckbeak's wings, however, when Harry was in Care of Magical Creatures and rode Buckbeak for the first time, Hagrid had told him to sit behind the wing joint, as he did in the films. However, this may have been because Hermione is sitting behind him.
• On the back cover of some editions, it said that Harry blew up his Aunt Petunia instead of Aunt Marge. This error was fixed in later editions of the same book.

Chapter 1: Owl Post

• In earlier editions of the book, the first page stated that A History of Magic was written by Adalbert Waffling, rather than Bathilda Bagshot.
  • This was rectified in later editions of the same book.

Chapter 2: Aunt Marge's Big Mistake

• When Harry leaves the Dursley's house after blowing up Aunt Marge like a balloon, he, at least in that moment, has the intention of never returning to the Dursley's home ever again. The bond of blood should have therefore been broken, making him fair game for Voldemort and/or the Death Eaters.

Chapter 3: The Knight Bus

• When Harry travels on the Knight Bus, 'Anglesey' is misspelled as 'Anglesea'.
• When Hedwig greets Harry in Leaky Cauldron, it says that she 'clicked her break' instead of 'beak'.

Chapter 4: The Leaky Cauldron

• When Harry is buying his books at Flourish and Blotts, it mentions that he is being served by the manager, but when Harry is staring at the book Death Omens, it says that he is being served by the assistant of the store. Although, it is possible that the manager was simply the assistant to the shop owner.
• The store clerk immediately moves to the cage with the "Monster Books of Monsters" inside them as soon as he sees Harry. However, as Care of Magical Creatures is only an elective for third year students, he had no reason to automatically assume that Harry needed that book without checking first.
• Mrs Weasley complains that Fred and George have not been made prefects. However, as only one male Gryffindor prefect would have been chosen from their year, it would have been impossible for both of them to be prefects.
• Mr Weasley says that Ron and Harry have ended up in the Forbidden Forest twice, but only Harry has ended up in the forest twice. Ron's first time into the forest was when he went with Harry to see Aragog in their second year, but in their first year, only Harry went into the forest for his detention; Ron was not there (he is in the film but not in the book). This error was corrected in later editions.
• From Mr Weasley's conversation at the Leaky Cauldron, Sirius has known that Pettigrew was hiding at Hogwarts for several months. But in the Shrieking Shack in chapter 18, Sirius says that he first learned about it the night he escaped from Azkaban. However, it is possible that Sirius may have been referring to someone else, perhaps Harry or Voldemort. Sirius would know that Harry is at Hogwarts by the time that he is reported to start talking in his sleep and he might have heard about the Chamber of Secrets incident when Hagrid was imprisoned here.

Chapter 5: The Dementor

• When Harry, Ron, and Hermione first find a carriage, and have stowed their luggage, they return to the platform to say goodbye to Mr and Mrs Weasley. Upon reentering the train, it is said that the three of them set off looking for an empty compartment and end up finding one at the very end of the train. Since the trio had already stowed their luggage earlier, there would be no need for them to go looking for an empty compartment. However, after Harry explains his situation with Sirius, it's revealed that Harry's Sneakoscope is in his trunk on the rack above them.
• 1 September in 1993 was the night of a full moon. Therefore, Lupin should not have been on the train, considering how later in the book he is unable to teach for the three days around the full moon.

Chapter 6: Talons and Tea Leaves

• Hermione's Time-Turner is a major secret that supposedly took a lot of persuasion to obtain. However, the reason it was necessary should not have been an out-of-place occurrence: any Gryffindor taking the Study of Ancient Runes would need to use one to attend their Friday Charms class that happens at the same time. Likewise, any Gryffindor who takes any combination of Divination, Muggle Studies, and Ancient Runes would require a Time-Turner since all of those classes occur at the same time on Wednesday mornings. However, one solution is that Hermione's case was an unusual one: perhaps most students would be told that they could not take those classes together in one year, but she persisted in asking for them. Alternatively, the timetable may have been reshuffled in past years when students wished to take conflicting classes, or be put into classes with other houses to ensure attendance. A student taking all of the classes, however, would render these fixes moot and require alternative methods - such as the Time-Turner.
• On page 101 of the US hardcover edition, Sybill Trelawney's name is misspelled as "Sibyll."
• Trelawney tells Lavender, "Incidentally, that thing you are dreading- it will happen Friday the sixteenth of October." In 1993, when this happens, October 16 was a Saturday.
• After Neville breaks his pink teacup, Trelawney asks Neville to get a blue one to replace it, as she likes the pink ones. She then proceeds to sweep up the shards of the first teacup with a feather duster and dust pan. It is unclear why she couldn't simply use a reparo charm to fix the first cup.

Chapter 8: Flight of the Fat Lady

• On page 117 of the UK paperback edition, when Harry is talking to Lupin about the Boggart and he mentions Voldemort, it says "The only person Harry had ever heard say the name aloud (apart from himself) was Professor Dumbledore" But in the Philosopher's Stone, Hagrid says, "Nah - can't spell it. All right - Voldemort." Although, Harry may have excluded Hagrid as he does not use the name habitually. Hagrid also whispered it begrudgingly.

Chapter 9: Grim Defeat

• During his substitution of the Defence Against the Dark Arts class, Snape says "That is the second time you have spoken out of turn, Miss Granger", but actually it is the third time she speaks out of turn. Although, Snape may have not counted the first time.

Chapter 11: The Firebolt

• Given that Remus Lupin had a transformation after Hallowe'en but before the following weekend, the full moon would have had to be sometime in the first week of November. Since a full moon occurs every month or so, the December and January full moons would also have occurred sometime around the first week of those months. Therefore, a full moon during the Christmas period is not possible. Yet, Dumbledore explains to Trelawney that Lupin's absence from the Christmas dinner is that he is not well again; implying either a transformation or post-transformation exhaustion, especially since Snape is mentioned as having brewed his potion for him.

Chapter 12: The Patronus

• When Harry gets back into the Gryffindor common room with his Firebolt given back to him after being tested for jinxes, the common room admires the broom. An unidentified Gryffindor tells Harry, "Ravenclaw'll have no chance, they're all on Cleansweep Sevens!" However, later in the book, Oliver Wood tells Harry that Cho Chang, the Ravenclaw Seeker, rides a Comet 260. It is possible, however, that the unidentified Gryffindor who told Harry this only meant that most of the Ravenclaws ride Cleansweep Sevens. Or, it could be due to the fact that they didn't know the Ravenclaw team's line-up before the match, so they just generalised from what they had seen in previous games.

Chapter 14: Snape's Grudge

• On page 285 of some versions of the US hardback edition, Snape's name is misspelled as "Snap".

Chapter 15: The Quidditch Final

• When Hermione realised that she had missed her Cheering Charms lesson, it is unknown why she didn't simply use the time turner to go back and make it to the lesson. The time turner can go backwards in time up to five hours. Charms was immediately before lunch, and Harry & Ron confronted Hermoine about the missed lesson immediately after lunch, so she was well within the 5 hour time limit.
  • Of course, according to the rules of time travel that will be established in this book's climax, everything that happens to the time traveller also happened in the original timeline. This means that, if Hermione had used the time turner in this instance, then from Harry & Ron's perspective, she would always have been at the Charm's lesson, meaning that Harry and Ron would not have had any reason to confront her about missing the lesson, meaning she would not have had the reminder to use the time turner in the first place.
• When Katie Bell is taking her second penalty shot, it says she put it past the Slytherin Seeker (Draco Malfoy), instead of the Keeper.
  • This error is corrected in later editions.

Chapter 16: Professor Trelawney's Prediction

• This chapter takes place in June 1994. Harry Potter reads a note from Hagrid and says, 'Buckbeak's appeal — it's set for the sixth.' The night after the Hippogriff's appeal, Remus Lupin is forced into a werewolf form by the full moon, which means that this happened on the night of June 6, 1994. The web page HP-Lexicon.org also backs this up. However, a brief look at lunar phase calendar sites such as 1994 and lunar phases in 1994 definitely shows June 9, 1994, as a new-moon night, which means that a full moon could not possibly rise three days earlier.
  • In addition, during that Christmas' luncheon, Dumbledore, when asked by Harry about Lupin not lunching with them, explicitly states that 'the poor fellow is ill again', alluding to a possible full moon the night before. This is impossible, however, if June's full moon rose on the 6th, as a lunar cycle is 29.5 days long (requires verification).
    • While it is possible that like dates and days not matching up in the Harry Potter universe to the real world, J.K. Rowling slightly adjusted the moon's phases to fit the story, it is highly unlikely that she made the lunar cycle shorter, as this would have major consequences on the tides, with likely catastrophic results.
    • It is also possible that Lupin had caught the flu, or any other - curable - disease. Again, this is highly unlikely, as Dumbledore states that he is ill again, indicating a similar incident having happened before.
• Before Harry and Hermione go back in time, it mentions that Buckbeak is tied to a tree. But when they go back in time, Buckbeak is tied to a fence. This error was fixed in later editions of the same book.

Chapter 17: Cat, Rat and Dog

• It says "Ron crawled to the four-poster and collapsed onto it". But when Professor Lupin comes in, it says "his eyes flickered over Ron, lying on the floor". This could not be, as Ron should still be on the bed. Crookshanks was on the bed, and 'on the floor beside him.... was Ron' Ron moves from this position to 'protect' Harry. 'If you want to kill Harry, you'll have to kill us too' at this point he is standing, 'clinging painfully to Harry to stay upright'.
• When Lupin tells Harry, Ron and Hermione that the Marauders' Map showed that someone was with them when they left Hagrid's hut, they argued that no one was. However, they knew that Scabbers was with them, and Harry already knows that the map shows animals, since among the characters he sees in the map when he first looks at it is Mrs Norris the cat.

Chapter 19: The Servant of Lord Voldemort

• Snape says in the Shrieking Shack that Lupin had not taken his potion that night, but it is explained that one must drink the Wolfsbane Potion the week before transforming — not on the night itself.
  • It may be that the potion must be continually consumed before the full moon to be effective, rather than just once the week before.
• During the climax, it is explained that it was Wormtail, not Sirius, who was the Potters' Secret-Keeper and, therefore, traitor. However, Dumbledore was the one who cast the Fidelius Charm in the first place. So he should have known from the beginning that it was Wormtail, not Sirius, who betrayed the Potters and therefore deserved to be executed by Sirius for his death eater affiliation. He could have use his position on the Wizengamot to advocate for Sirius's exoneration after Voldemort's first downfall, or clear the air after Sirius escaped at the beginning of this book. However it is possible that a Secret Keeper is themself secret; with Sirius claiming the role as the most obvious choice and decoy from Pettigrew, only those told the Secret would know who the Secret Keeper for the Secret was. As it is, we don't know enough about how the spell works and its rules.
• Sirius Black says that Voldemort has been in hiding for fifteen years. He's actually been in hiding for twelve years (almost thirteen at the time that he says it), about the same amount of time since Black was imprisoned. Voldemort went into hiding right after he was ripped from his body after failing to kill Harry. Of course, Black could just be rounding off to an approximated number (fifteen years), but this seems unlikely since he keeps talking about being in Azkaban for twelve years, being that the two time frames are almost exactly the same. Sirius also says to Pettigrew 'you haven't been hiding from me for twelve years, you've been hiding from Voldemort's old supporters'.
  • This is corrected in later editions.

Chapter 20: The Dementors' Kiss

• When Lupin, Pettigrew and Ron are tied together, they are described as 'looking like contestants in a six-legged race', but it would actually be a four-legged race, as each pair of bound legs counts as one leg.
• In the US paperback edition, when exiting the tunnel that lead out of the Whomping Willow, the group was in the following order: Crookshanks, Lupin, Pettigrew, Ron, Snape, Sirius, Harry, and Hermione. Later, when Hermione uses the Time-Turner, Harry and Hermione see themselves coming out in the order: Lupin, Ron, Pettigrew, Hermione, Snape, Harry, and Sirius.
  • This is corrected in later editions of the book.

Chapter 21: Hermione's Secret

• On page 287 of the UK paperback edition, Dumbledore is speaking to Harry and Hermione and tells them, "There is not a shred of proof to support Black’s story, except your word – and the word of two thirteen-year-old wizards will not convince anybody," but Hermione's birthday is in September, so she's 14 years-old at this point. However, this may not be considered a mistake, as it could be explained simply by Dumbledore not remembering Hermione's birthday.
• When Harry and Hermione leave from the hospital wing using the Time-Turner, Dumbledore says it is ten minutes until midnight, but on the way back to the ward after they rescue Sirius, they hear Dumbledore say to the other versions of them that it is five minutes to midnight.
  • Corrected in later editions, making Dumbledore say "five minutes to midnight" the first time, instead of ten.

Chapter 22: Owl Post Again

• In June, Fred and George Weasley find out they have scraped "a few O.W.L.s apiece." However, in subsequent books, it is firmly established that O.W.L. results are sent home by owl and are not received until August.
• On page 311 of some editions, it said "Dumblefore" instead of "Dumbledore". This typographic error was rectified in later editions.

Harry Potter and the Goblet of Fire

• In the early printings of the Scholastic edition, there are some books which were bound incorrectly, the spine and cover having been bound inverted. Upon opening, one notices that the text seems inverted, that the first page ones sees is really the last of the book.
• 1 September 1994 was Sunday in the book but if 30 October 1994 was Friday, then 1 September would have to be Tuesday if you counted from that day to the 30 October. The book not only states 1 September was Sunday, but that the 2 September was Monday and that three days later on Thursday, Harry attended Defence Against the Dark Arts when in logically it would be Tuesday 1, Wednesday 2 and Saturday 5 September. The only way it could work is if both September and October were only exactly 4 weeks (or 28 days) long.

Chapter 1: The Riddle House

• In the American version, there are repeated references to a planned murder, with lines such as "... one more death and our path to Harry Potter is clear" and "One more murder… my faithful servant at Hogwarts…" Yet, there is no indication that anyone else is murdered that was part of this plan. Bertha Jorkins was already dead, Frank Bryce was only a victim of circumstance, and Barty Crouch was originally kept alive and only killed because he had escaped and become a liability.
  • The British version specifically said curse; not murder. This was also corrected to "curse" in later printings of the American versions.

Chapter 2: The Scar

• The narration mentions at one point that Harry "had only found out that Sirius was his godfather two months ago," when in fact it had been on the December Hogsmeade trip (in other words, eight months ago) when Harry overheard that Sirius was his godfather. It would be more accurate to say he "had only found out that Sirius was innocent two months ago."
  • Additionally, on the same page, Harry mentions that he had met Pettigrew "the previous year" rather than "two months ago.", though it is likely that referred to school year rather than calendar year (which would mean that the 1994–1995 school year was treated as the current year, even though it hadn't actually begun yet).
• In the letter Harry writes to Sirius he mentions Dudley throwing his PlayStation out the window; however the PlayStation wasn't released until December 1994 in Japan and September 1995 in Europe.
  • Regarding that, J. K. Rowling has stated "I can’t work PlayStations. I’m no good at these things."
  • One in-universe explanation is that Dudley's parents may have bought one of the earlier available PlayStation prototypes designed for game designers, some of which were known to have been sold to private consumers. Alternatively, the PlayStation may have been released earlier in the Harry Potter universe, or Harry, due to his lack of interest in Muggle technology, might have confused the PlayStation with a similar console.

Chapter 4: Back to the Burrow

• Mr Weasley puts a pinch of Floo Powder into the fire for their group to return to The Burrow, but in Chamber of Secrets everyone has to use Floo Powder individually to travel.
• Mr Weasley uses magic to deflect something that Vernon Dursley has thrown at him. In The Chamber of Secrets, Harry receives a warning from the Ministry of Magic for using magic in the presence of Muggles and also because he is underage and away from Hogwarts, even though it was Dobby who used magic, not Harry. We later learn that this is because the Ministry doesn't know when a specific wizard uses magic, but rather, where it is used. Since the Ministry knows Harry is the only wizard living in that general area, any magic performed is assumed to come from Harry. So why wouldn't Harry have received a letter after Mr Weasley performed magic in the Dursleys' home?
  • This might be because Mr Weasley notified the Ministry that he was going there, so they couldn't just assume it was Harry.

Chapter 5: Weasley's Wizard Wheezes

• While cooking, Mrs Weasley pours a cream coloured sauce from her wand. This breaks Gamp's Law of Elemental Transfiguration, which states that food cannot be created by magic. This could be explained as that Mrs Weasley is Summoning the sauce rather than conjuring it from nowhere.
• After Hermione stops Ron from talking about Sirius Black in front of Ginny, it is stated that the only people who knew about his innocence are the trio and Albus Dumbledore, but Remus Lupin also knew and the trio knew that. It is also stated that Ron helped Sirius escape, even though he was in fact in the Hospital Wing recovering and was thus unable to accompany Harry and Hermione in the Rescue of Sirius Black and Buckbeak.

Chapter 6: The Portkey

• Mr Weasley cites Diagon Alley and Platform Nine and Three-Quarters as two places that muggles cannot penetrate. However, neither of these are truly muggle-proof. In Deathly Hallows, during the chapter "The Prince's Tail," it is shown that Lily Evans' parents and sister were able to enter Platform Nine and Three-Quarters. Also, in Chamber of Secrets, Hermione's parents are in Diagon Alley with their daughter, and in fact, Arthur Weasley even strikes up a conversation with them.

Chapter 7: Bagman and Crouch

• When Fred and George bet on the Quidditch match with Bagman, it says Fred put the paper with their wages in his robes, but Fred was wearing Muggle clothing.
• When the Weasleys, Hermione, and Harry arrive at the camp site for the Quidditch match, they have to use a map to find where they set up their camps. Yet Percy, Bill, and Charlie are able to find them right away after apparating in the woods. This is proved by Percy saying, "Just Apparated, Dad" as soon as they emerged from the woods. It seems impossible that the three could have found their camps that quick, unless Mr Weasley had sent a message to his sons while collecting wood for their fire.
  • However it is said that their camping spot was located right next to the main path, so Percy, Bill and Charlie may just have got lucky.
  • It is also possible that the three eldest children did in fact go to find a map, and Percy was referring to them Apparating a short while ago.
  • Since Percy is a very proud person who has just left Hogwarts, he may be simply bragging about his ability to apparate, while his younger siblings cannot.

Chapter 8: The Quidditch World Cup

• In Quidditch Through the Ages, it says that the first-ever World Cup was in 1473, with a match being held every four years. Yet, the World Cup in 1994 is number 422. There cannot be 422 World Cups in 521 years with a four-year gap in between.
  • The period of years in between Quidditch matches in 1473 may have been slightly different, or the years may have been counted differently.

Chapter 10: Mayhem at the Ministry

• In the American paperback edition on page 148, Harry asks Ron if he can dump his things upstairs in his room. It then states, "'What's up, Harry?' said Ron, the moment they had closed the door of the attic room behind them." In the Harry Potter and the Chamber of Secrets American paperback edition, on page 41, Ron says "... I'm right underneath the ghoul in the attic," referring to his room. Therefore the sentence in Goblet of Fire where he closes the attic door (to his room) does not make sense because that is where the ghoul resides.
  • Although with The Burrow being such a haphazard building, it is likely that it contains more than just one attic (an attic referring to a room beneath the eaves). Alternatively, attic rooms can have space between them and the roof, depending on the shape of the room. In such a case Ron's room may be called the attic room and still have attic space above it - as it would all still be beneath the eaves.
  • It is also possible that, due to the familiarity with the ghoul, the Weasleys managed to move it into a different room over the course of two school years. An example that supports this would be Ron's plan for the ghoul to take up residence in his room while he was away searching for Horcruxes with Harry and Hermione.

Chapter 11: Aboard the Hogwarts Express

• In the Scholastic Edition, in the 28th line of the Sorting Hat's new song, Hufflepuff is spelt as "Hufflepujf."

Chapter 14: The Unforgivable Curses

• Near the beginning of the chapter, Neville is assigned the task of disembowelling horned toads as punishment from Professor Snape. When Hermione teaches him the Scouring Charm to remove the filth from under his fingernails, they're referred to as "frog guts". However, the horned toad is actually a species of lizard, despite the name.
  • Since this was from Harry's point of view, however, he might not have known that fact and simply assumed the horned toad was a species of frog.

Chapter 15: Beauxbatons and Durmstrang

• The notice that says classes will end a half hour early for the arrival of the Durmstrang and Beauxbatons students states that 30 October, 1994 is a Friday. However, it was really a Sunday.

Chapter 16: The Goblet of Fire

• Curiously, 1994 was the second year in a row in which Hallowe'en fell on a Saturday. In 1993, Professor Trelawney's prediction to Lavender Brown warned her that her worst fears would come true on Friday, 16 October. In 1994, 30 October was the date of the arrival of the Durmstrang and Beauxbatons students and was a Friday; the same day of the week it would have been in 1993 as the 30th fell exactly two weeks after the 16th. That is not possible because the same date does not fall on the same day of the week two years in a row.

Chapter 17: The Four Champions

• Harry is said to be facing competitors who'd had three years more magical education than he had. But Cedric was only two full school years above Harry being 17 years old, so he'd only had two years more magical education than Harry, having been in his 7th and final year of Hogwarts. However, Harry could have simply been referring to their ages and not their exact years of magical knowledge.

Chapter 19: The Hungarian Horntail

• As Hagrid takes Harry to see the dragons and he stops to pick up Madame Maxime, Harry wonders to himself "Had Hagrid wanted to show him Madame Maxime? He could see her any old time he wanted...she wasn't exactly hard to miss....". But this implies that Madame Maxime is easy to miss, the opposite of what is intended. It should say something to the effect of "she wasn't exactly easy to miss".

Chapter 20: The First Task

• In the first task, nowhere has it been stated that one could not retrieve the Golden egg through the use of a Summoning Charm, but none of the champions even attempted this most simple system to do so. However, it is stated that the first task was designed to test the champions' daring and courage; thus, using a Summoning Charm would be too easy — almost to the point of cheating. It is possible that use of this spell would have resulted in a bottom score, or that there were enchantments on the eggs to prevent Summoning.

Chapter 23: The Yule Ball

• Harry and the Weasleys abandon their snowball fight return to the castle at 7:00 pm, when it had become "difficult to aim", implicitly because it had gotten dark. However, in the Scottish Highlands, the sun sets around 3:30 pm on December 25. As such, it would have already been completely dark when Hermione went up to the castle at 5:00 pm, let alone two hours later.
• In the European and Canadian versions of the book, Snape shouts, "Ten points from Hufflepuff, Fawcett! And ten points from Ravenclaw too, Stebbins!" Really, Fawcett is in Ravenclaw, and Stebbins is in Hufflepuff.
  • It may, of course, be that Snape, angry as he was, mixed up the two students' affiliation to the houses. The American version corrects this error, but in a deleted scene from the film, included in the uncut DVD, Fawcett is again the Hufflepuff and Stebbins the Ravenclaw.

Chapter 26: The Second Task

• In the Second Task, Viktor Krum transfigures his top half of his body into a shark's head to swim underwater without the need of air. However in Quidditch Through the Ages it clearly states that when transfigured into an animal, the wizard loses all sense of human thought and becomes the animal until another wizard can transfigure them back. Krum who transfigured his head into a shark really should have attacked Hermione and not been able to do the task at all. Although, it is possible that due to the fact that Krum only partially transfigured himself, he might have some control over his thoughts and actions.

Chapter 28: The Madness of Mr Crouch

• Barty Crouch Snr mentions that his son got twelve O.W.L.s. Once again, this is inconsistent with the time-table clashes from Prisoner of Azkaban.
  • However, given Crouch Snr's damaged state of mind, he could have just been rambling insanely.
  • Another possibility is that it is not necessary to take a class in order to sit an O.W.L. This is logical since Remus Lupin mentions in Deathly Hallows that until Voldemort took over the Ministry, parents were allowed to educate their children at home, though virtually all British magical children attended Hogwarts. These students would presumably need the credentials given by an O.W.L. or an N.E.W.T. in order to obtain employment in many occupations. It is thus possible that a highly motivated student may be able to do "independent study" to achieve an O.W.L. or that a student was already so familiar with the Muggle world, for example, that they could easily pass an O.W.L. in Muggle Studies without attending classes.
  • It could also be explained as Barty Crouch Junior being provided with a Time-Turner, similar to how Hermione is provided with one in the previous book.
• In some printings, the spell to revive Krum and Crouch from unconsciousness is ennervate. The correct spelling is rennervate, since ennervate would have the opposite effect (corrected in later editions).
• On page 550, Cedric Diggory discusses with Harry what the third task of the Triwizard Tournament might be. He says Fleur keeps talking about underground tunnels and how she believes the champions will have to find treasure. Harry believes that wouldn't because he could borrow a "niftier" from Hagrid. It appears to be a spelling mistake for the magical creature, the niffler, which the fourth years recently learned about in a Care of Magical Creatures lesson.
  • Harry may have just forgotten the correct name of the creature since there only was one lesson with nifflers up to this point. However, it seems unlikely because Harry Potter is usually shown to retain information from most of his classes.

Chapter 29: The Dream

• Harry, Ron, and Hermione were supposed to call Sirius "Snuffles". Hermione calls Sirius "Snuffles" but she then calls him "Sirius" twice. It is likely, however, that Hermione simply made a mistake.
• During the meeting between Fudge, Dumbledore, and Moody, Fudge is mistakenly referred to as both "Crouch" and also as his first name, "Cornelius."

Chapter 31: The Third Task

• Voldemort's entire plan (to return in secret and build up his army in secret before revealing his return on his own terms) falls apart if the spectators can witness the third task. If everyone sees Harry and Cedric grabbing the Triwizard Cup and then disapearing, everyone would notice something is up. However, by all logical accounts, the Third Task should have been visible to spectators. The hedges in this chapter (which were set up in the Hogwarts Quidditch Pitch) were described as being 20 feet high, and in Chapter 2 of this book ("the Scar"), quidditch goal posts were said to be 50 feet high. It is highly unlikely that the stands would be placed below the goal posts, as this would make watching the match very inconvenient. Thus, those in the stands should have been seated 30 feet above the top of the hedge maze, giving them plenty of height with which to see into the maze. For that matter, making the inside of the maze invisible to spectators defeats the entire reason the Triwizard Tournament was brought back after more than a century: Having enough safeguards that the risk of death was minimal.

Chapter 34: Priori Incantatem

• Toward the end of the book when Voldemort puts the Imperius Curse on Harry, the book says "for the third time in his life," but toward the middle of the book it states Harry had the Imperius Curse put on him four times by Moody (Crouch, Jr.).
  • This, however, may have been a reference to the number of occasions and situations on which it was used rather than the exact number of times the curse was placed on him.
• In what is now known as the "Wand Order Mistake," when Harry and Lord Voldemort's wands engage in Priori Incantatem while in the graveyard, James Potter exits the wand before Lily Potter. It has always been said that James died first as he was trying to give Lily and Harry time to flee, and since victims of Lord Voldemort were exiting the wand in reverse order of being killed, it was thought to have been a clue from J.K. Rowling.
  • Rowling later said that "late night writer's fatigue" was the reason, and the error has been fixed in later editions.
• Prior to Bertha Jorkins coming out of Voldemort's wand there should have been indication of Voldemort making a Horcrux with her death, after she appears but before Lily appears there should also have been some indication of the methods Voldemort used to break her memory charm. It is of course possible he used another wand in both cases but unlikely he would have changed wands shortly after killing Bertha.

Chapter 35: Veritaserum

• On page 594 in the first edition of the Canadian paperback and page 685 of the first edition American hardcover, when Dumbledore is questioning Barty Crouch, it says, "'How did your father subdue you?' said Dumbledore. 'The Imperius curse,' said Moody." Crouch is mistakenly referred to as Moody in this sentence because it was after Barty Couch had already returned to his original physical state (no longer an impersonation of Moody). Crouch had already been referred to by his real name earlier on that page, and the real Moody was lying stunned at the bottom of the trunk in his office. 
• Barty rigged the entire tournament to fool Harry into making contact with a Portkey, even though a Portkey can literally be anything. Had Crouch simply made a Portkey of his bedsheets or a schoolbook, Voldemort could have returned months sooner.
  • One possible explanation is that, much like apparition, portkeys do not work into or out of Hogwarts grounds unless the Headmaster explicitly authorises them. This would also avoid a potential plothole: If the Third Task was not visible to spectators, how would the judges determine the winner if it was disputed who reached the cup first? Having the cup teleport the first one to touch it to the start of the maze is a foolproof way of knowing who touched it first. Thus, Voldemort had to wait patiently for Dumbledore to temporarily lower the anti-portkey defences in and around the Hogwarts Quidditch pitch, and only then could Crouch Jr (disguised as Moody) volunteer to perform the task of turning it into a portkey.
  • Furthermore, as Sirius explains in the next book, Voldemort wanted to keep his return a secret (at least at first) and Harry's unexplained disappearance would make that harder to achieve. It is likely that Voldemort had been planning to transport Harry's dead body back to the maze via the portkey so as to pass his death off as an accident. Sirius was therefore ultimately correct in suspecting that the intention of the person who entered Harry in the tournament was to "attack [Harry] and make it look like an accident", just not in the way he'd anticipated.

Harry Potter and the Order of the Phoenix

• At least twice in the U.S. audiobook edition, Hermione pronounces the acronym for the Society for the Promotion of Elfish Welfare, S.P.E.W., as "spew" when speaking to Ron, despite her strong objections in the previous novel when Ron pronounced it this way, insisting on each letter being enunciated out loud.
• In the book, classes begin the day after the Start-of-Term Feast. However, September 1, 1995 was on a Friday, which would mean that classes started on the weekend, which is unlikely.
• Sirius Black told Harry Potter that Bellatrix ran in the same crowd as Severus Snape while at Hogwarts, but her date of birth makes this impossible. Bellatrix would have attended Hogwarts from 1962 to 1969, or possibly 1963 to 1970, depending on which month in 1951 she was born in, whereas Snape began his schooling in 1971.
  • This may simply be an error since J. K. Rowling has admitted that maths is not her strong suit.
  • Another possible explanation could be that both Bellatrix and Snape went around with the same type of people, some of whom may have overlapped depending on age. For example, Lucius Malfoy was mentioned to be a prefect during Snape's Sorting in Deathly Hallows. However, this is rather unlikely as Bellatrix was heavily implied to be extremely active in Voldemort's war throughout the 1970s.
• It is mentioned that Remus, rather than James, was the male Gryffindor prefect in Harry's father's year. However, Hagrid mentions in Philosopher's Stone that James and Lily were Head Boy and Girl at Hogwarts. Since it is implied that the Head Boy and Girl are chosen from the prefects, this does not work.
  • Although it is implied that the Head Boy and Girl are chosen from the prefects, it is never explicitly stated, so James could have been Head Boy without being a prefect.
  • If James had been Quidditch Captain, he could have become Head Boy through that, as Quidditch Captains have equal status with prefects.
  • Hagrid could simply have been mistaken in thinking that James had been Head Boy.
• It states that after watching Ginny play it was Harry's first time watching Quidditch in the stands but Harry would have watched all the other matches that didn't involve Gryffindor (all matches since his first year at Hogwarts).

Chapter 2: A Peck of Owls

• After Harry tells Uncle Vernon about Voldemort and Uncle Vernon tells Harry to get out, Dumbledore sends Petunia a Howler which says "Remember my last, Petunia" referring to the letter Dumbledore had left on the doorstep with baby Harry. Later, in Chapter 37, Dumbledore explains that Petunia "might need reminding of the pact she had sealed by taking [Harry]". However, in chapter 5 of the Chamber of Secrets, after Harry and Ron crash the Ford Anglia into the Whomping Willow, Dumbledore says he will "be writing to both [their] families tonight". This means that the Howler was referring to this letter about the flying car rather than the letter written by Dumbledore on the night of Lily and James' death as intended.
• Mrs Figg tells Harry that she had stationed her cat, Mr Tibbles, to keep a watch on the Dursley house. However, in the first book, it gives a short list of Mrs Figg's cats, one of which is simply Tibbles, as opposed to Mr Tibbles.
  • A possible explanation is that Harry some or all of her cats' names mixed up, which is understandable as she has so many. Also, it's possible that they both refer to the same cat, only she calls it by slightly different names.
  • She could also be referring to the same cat, but changing whether or not to use the honorific. Many people switch between using 'Mr' or not before a name.

Chapter 3: The Advance Guard

• When the Advance Guard arrives at 4 Privet Drive to take Harry to 12 Grimmauld Place, Harry is already in trouble for casting a Patronus Charm in the presence of a Muggle. Yet, Tonks casts several spells (Lumos, a packing spell, Scourgify and Locomotor Trunk) and Moody casts a Disillusionment Charm on Harry while they are still at 4 Privet Drive. Lupin had clearly stated that they were not using the Floo Network because they were being watched (by the Ministry), so of course the Ministry was not aware of any Wizards that are allowed to do magic inside Harry's house. If the Ministry can detect magic, and Harry is the only known wizard in Little Whinging, then he should have either had another owl sent from the Improper Use of Magic Office or the uses of those spells should have been brought up at some point during his trial. Possible explanations include the fact that there were no Muggles present at the time, or that unlike Dobby, magic used by registered wizards does not activate the Trace, however this is inconsistent with the seventh book, when Harry is told they had to escape using Polyjuice Potion and physical transport because using any magic at all around Harry would alert the Ministry to his presence. However that could be because of the rise of Voldemort at the time meaning heightened security around Harry - including making the Trace far more sensitive to spellcasting.

Chapter 6: The Noble and Most Ancient House of Black

• A nest of dead puffskeins is discovered in 12 Grimmauld Place under a sofa. But according to some information, it's impossible, because the puffskeins are too big for going under a sofa and making nests.
  • This does, however, depend on the type of sofa - some do have larger gaps beneath them than others, especially older sofas, which Grimmauld Place may well have had. Additionally, the Puffskeins could have made a nest in the underside of the sofa which spilled out into the space beneath, like rats.
• Sirius explains that he has been couped up in 12 Grimmauld Place since the start of the Second Wizarding War, since he is wanted by the Ministry and his dog form is now known to the death eaters, as Wormtail would most likely have told them about it. However, it is revealed in Deathly Hallows that Mad-Eye Moody has a large supply of polyjuice potion on permanent standby in case of emergencies (Hermione borrowed some of that potion for their upcoming horcrux hunting mission, since Moody obviously wouldn't need it anymore). So it is unclear why Moody didn't simply lend some of his polyjuice potion to Sirius so he could exit the house every once in a while, and perhaps even go on missions for the Order, without anyone outside of the order recognising him.

Chapter 8: The Hearing

• During Harry's hearing, Cornelius said that he blew up his aunt three years ago. However, the incident when Harry inflated Marjorie Dursley occurred almost exactly two years previously.
  • Although, this may be a mistake on Cornelius's part, and could show that he was not told accurate information, he had forgotten the date Harry blew up Aunt Marge, or that he was desperate enough to give away the wrong information; the second theory is most probable.
• When the Wizengamot is considering the verdict of Harry's trial, Madam Bones states 'Those in favour of clearing the witness of all charges?' - As he has been accused of a crime and the subject of the trial, Harry should be referred to as 'the accused'. A witness attends court to give evidence only.

Chapter 9: The Woes of Mrs Weasley

• Ron's prefect badge is described as scarlet and gold. Page 162 of the American paperback edition states, "A large P was superimposed on the Gryffindor lion. He had seen a badge just like this on Percy's chest on his very first day at Hogwarts." However, Percy's badge in Philosopher's Stone is described as silver with a P on it (later editions of the first book are fixed).
• When Alastor Moody shows Harry the Order of the Phoenix photograph, he mentions that Caradoc Dearborn disappeared six months after the picture was taken, and implies that this was during the height of the First Wizarding War. However, he also mentions that Marlene McKinnon was killed two weeks after the picture was taken. Lily's Letter in Chapter Ten of the Deathly Hallows dates Marlene's death in late July or early August of 1981, putting Caradoc's disappearance around January 1982—three months after the end of the war.
  • However, it is possible that some Death Eaters continued to fight in Voldemort's name, similar to the group that tortured the Longbottoms.
• In the American paperback edition, on page 161, when talking about the old Defence Against the Dark Arts teachers, Harry says, "One sacked, one dead, one's memory removed, and one locked in a trunk for nine months," referring to Lupin, Quirrell, Lockhart, and Moody respectively. However, according to the Prisoner of Azkaban American paperback edition, on page 423, Lupin did not get sacked — he resigned.
  • However, Harry could have interpreted Lupin's resignation as forced by Snape's revelation of his lycanthropy and therefore considered it the same as a sacking. Also, Fred does not mention either of his first two Defence Against the Dark Arts teachers, though it is possible that those two simply resigned and nothing particularly bad happened to them, thus no mention.
  • Lupin was not officially sacked, but there was pressure from the School Board for him to resign.
• When asked to look into a desk in another room in Grimmauld Place, Mad-Eye Moody was able to determine it contained a Boggart. However, Remus Lupin established that nobody knows what a Boggart's true form is, as it always shapeshifts into the deepest fear of whomever sees it. It seems unlikely that the Boggart could have taken the form of Moody's greatest fear as he was not in the presence of the Boggart, so he must have seen it in it's true form and known what it was.
  • It is possible the Boggart took the form of Moody's greatest fear and thus he was able to recognise it as a Boggart, but it has never been established that Boggarts can take on a subjective form if observed indirectly.
  • Because of this scene, it has also been said that Mad-Eye is the only person to have seen a Boggart in its true form.

Chapter 12: Professor Umbridge

• Ron says "That's the worst Monday I've ever seen" in reference to his and Harry's schedule for the first day of classes. As school commences with the feast on 1 September, this first day of classes would fall on 2 September. However, at the end of Chapter 6, it is written that the night before Harry's trial is a Wednesday. Thus, Harry's trial, which takes place on 12 August, falls on a Thursday. So 2 September would actually have to be a Thursday, as well. (And in 1995, 12 August and 2 September were actually Saturdays.)
• When Umbridge first puts Harry in detention she tells him to be in her office at 5:00. On the following day, when Harry goes to detention, the book says that he went to dinner before then, which means that dinner at Hogwarts starts at least at half past four, which is unlikely. However, dinner isn't always referred to as the 'last meal of the day' - in other books Harry, Ron and Hermione have headed to dinner as soon as afternoon lessons have finished. So it is conceivable that dinner at Hogwarts is served fairly early as lessons in UK secondary schools tend to finish between 3.30pm and 4pm. 'Dinner' does refer to the evening meal as the book refers to the midday meal as 'lunch'. Some British people call the lunchtime meal 'dinner' and the evening meal 'tea' but the books call the meals 'lunch' and 'dinner'.

Chapter 15: The Hogwarts High Inquisitor

• In the UK audiobook version the line "Then you get "P" for "Poor" and "D" for "Dreadful"" is rendered in Hermione's voice, when it is obvious from context that Fred is the speaker.

Chapter 16: In The Hog's Head

• Dennis Creevey shows up for the meeting in the Hog's Head. However, Dennis would only be a second year, and therefore unable to visit Hogsmeade.
  • He could, however, have sneaked out of the school with his brother, although what with Filch guarding the entrance and the Creeveys not having been notified of any secret passageways, this seems unlikely (unless they discovered one by chance).
  • However, Fred and George were both aware of who Hermione was intending to recruit (having been recruited themselves) and could have shown him one of the secret passageways.

Chapter 18: Dumbledore's Army

• Harry summons the escaping bullfrog with Accio in charms class. However Rowling said "Accio only works on inanimate objects" after the Fantastic Beasts movie was released.
• When Cho and Harry go to Hogsmeade together, she recalls their first match against each other "in the third year."  As she is a year older than him it should have been "in your third year."
  • She may have been referring to the third year they had been on their house Quidditch teams, Gryffindor and Ravenclaw, respectfully.
• February 14, 1996 was a Wednesday. There should not have been a Hogsmeade visit on Valentine's Day.

Chapter 19: The Lion and the Serpent

• Harry refers to the Dark Marks on the arms of the Death Eaters as scars when they are actually brandings.

Chapter 22: St Mungo's Hospital for Magical Maladies and Injuries

• In an error unique to the U.S. audiobook editions of Harry Potter and the Order of the Phoenix, when Harry first arrives at 12 Grimmauld Place following his vision of the attack on Arthur Weasley, the line "Back again, the blood-traitor brats! Is it true their father's dying?" is rendered in the loud, screechy voice of Sirius Black's mother. Based on context clues, however, particularly the fact that this line is immediately followed by Sirius shouting "Out!" and Kreacher shuffling out of the room, it seems clear that it was actually Kreacher that uttered the insults and not Mrs Black.

Chapter 23: Christmas on the Closed Ward

• Harry states that Dobby left the Malfoys to give him warnings two years previously, but it was in fact three years previously (two years previously would mean it happened in Harry Potter and the Prisoner of Azkaban).
• Sirius could have easily just called Kreacher's name in order to force Kreacher to apparate directly to his side (just like Harry would do in Half-Blood Prince and Deathly Hallows), so he could be questioned about his whereabouts. But Sirius never attempts this simple method of finding him or even considers it.

Chapter 25: Occlumency

• Snape states that eye contact is often essential to legilimency, and that Harry is only an exception because of the telepathic link between him and Voldemort. In that case, couldn't legilimency in all other cases be easily blocked by a simple pair of sunglasses?

Chapter 26: Seen and Unforeseen

• When Snape calls Voldemort "the Dark Lord," Harry makes an accusatory statement, claiming to have only heard the Death Eaters call him that, but in Prisoner of Azkaban, Professor Trelawney, who has never been suspected of being a Death Eater, called him that. Even earlier, in Chamber of Secrets, Ginny Weasley wrote a poem that referred to Voldemort as "the Dark Lord." Another year before that, in Philosopher's Stone, Ollivander also called him "the Dark Lord" as he talked about his past achievements.
  • However, Trelawney's use of the title "the Dark Lord" was used largely for poetic effect rather than out of loyalty.
  • It is possible that Harry forgot these examples due to his anger at Snape, or selectively ignored them in favour of accusing Snape of being a Death Eater.
• Harry mentions that he gave the interview on the last Hogsmeade weekend. He did it on 14 February, which was a Wednesday in 1996.

Chapter 28: Snape's Worst Memory

• Draco Malfoy takes away points from Gryffindor and Hufflepuff when he catches Hermione saying what she really thinks of Umbridge. Then a conversation ensues in which Ernie Macmillan says that prefects can't take away points, even though Percy Weasley takes away points in the second's book Chapter 2 when he discovers Ron coming out of Moaning Myrtle's bathroom. In later editions this is fixed to say that prefects cannot take points away from other prefects, but this clarification is not reflected in the Jim Dale or Stephen Fry read audiobook editions of Book 5.
  • It may also be that Percy merely intended to report the trio's actions to someone who could take those points away, rather than doing it himself.
• After Harry has seen his father bully Snape in a memory, he remembers Professor McGonagall saying that James and Sirius were troublemakers at school but no more so than the Weasley twins. This is incorrect. She said in Prisoner of Azkaban that she had no memory of anyone else being so troublesome, and Hagrid said Fred and George could have given them a run for their money.
  • One possible explanation is that McGonagall's earlier statement was a hyperbole. Regardless, it was still not her who said that they were like Fred and George. (It actually just states in the book that Harry imagined them as precursors of Fred and George, so McGonagall didn't really imply it.) A large part of the community also refers to the twins as the successors of James and Sirius.
  • Another possible explanation is that both the pairs were the most known trouble-makers of different decades.

Chapter 30: Grawp

• In the American hardcover edition, Harry and Hermione find seats in the topmost row at the Quidditch match, but when Hagrid comes to tell them about Grawp, he squeezes his way through the row behind them. If Harry and Hermione are in the topmost row, there cannot be a row behind them (corrected in later editions). But there could be a walkway behind the top row.

Chapter 31: O.W.L.s

• It is stated that the practical Astronomy O.W.L. began at 11:00 pm, and Harry observed Venus one hour later (12:00 am). However, Venus can only be observed shortly before sunrise or shortly after sunset; it can never be seen at midnight. Harry was also filling in his star chart with the stars in the constellation of Orion. However, Orion would have set before 11:00pm on that date. Also, Hogwarts is somewhere in the Highlands of Scotland (according to the movie of Prisoner of Azkaban, it's near Dufftown in Moray); at that latitude, in the two months either side of June 21, the sky never gets completely dark. There is at least one website showing that sunset on the day of the examination would be about 11pm — the time the examination is supposed to start. It would be unlikely to be dark enough to observe any but the brightest stars.
  • The telescopes may be charmed to show every star regardless.
  • Harry could have mistaken Venus for a different celestial body.
• During the Ordinary Wizarding Level examinations, Hannah Abbott was doing her Transfiguration practical at the same time as Harry Potter. This is odd since the examinations are done by surname, meaning that Hannah should have finished a while ago, unless she was a rather incompetent student, or unless she had a fit of anxiety in the middle of the examination and had to be calmed, which could take time, and then resume the exam when Harry started his. (It is implied that Hannah was given a Calming Draught).

Chapter 34: The Department of Mysteries

• During the trip of Ministry of Magic with his friends, it was left out why there was no Order members there on watch duty, as in the beginning of the book, they mentioned about constantly being on watch duty, day and night.
  • It can however be assumed that, just as the defences on the Department of Mysteries seem to be impaired, the Death Eaters (who had already entered the Department) had removed the watching Order Members when they broke in to wait for Harry.

Chapter 35: Beyond the Veil

• In the UK paperback celebratory edition, the first line of the sentence which runs from page 710 to 711 is repeated, first on the bottom of page 710 and again at the top of page 711. The line reads, "Harry saw the look of mingled fear and surprise on his god-".

Chapter 36: The Only One He Ever feared

• Dumbledore sets up a portkey to teleport Harry directly into the Headmaster's otherwise impenetrable office. Earlier, he sets up a portkey in mere seconds to teleport Harry, Hermoine, and the Weasleys from his office into 12 Grimmauld Place. This could arguably be considered a serious security risk to Hogwarts. While you cannot apparate into or out of Hogwarts grounds, portkeys hardly seem like an inferior alternative, especially since, as Dumbledore demonstrates, they can be set up in mere seconds if you know exactly what you're doing. Couldn't Voldemort (during the First Wizarding War when he didn't need to worry about staying hidden) just portkey his way right next to Dumbledore's bed in the wee hours of the morning, and perform the killing curse on Dumbledore before he even wakes up?
  • One possible explanation is that, like the aforementioned mistake in Goblet of Fire, only the Headmaster can set up a portkey into or out of Hogwarts grounds. However, even that is not ideal in this case, because in the moment when he set up the Portkey to take Harry back to his office, he is not the Headmaster anymore; Umbridge is.
    • Perhaps Umbridge, being the incompetent witch that she was, did not fully understand that the Hogwarts castle itself does not merely bend to the will of whoever the Ministry says is Headmistress. Some type of ritual or spell must be performed in order for the castle and its various enchantments to recognise a person as headmistress and grant her the appropriate control over the castle's enchantments. Other teachers, such as McGonnigal or Flitwik, may know how to properly install a new Headmaster, but they willingly withheld this information from Umbridge.

Harry Potter and the Half-Blood Prince

• Harry's sixteenth birthday happens on 31 July, 1996. Looking at any full moon calendar, in that year the full moon was on 30 July. Remus Lupin was recovering from the after effects of his werewolf transformation and it is therefore difficult for him to go to birthday parties. It is said, though, that he was looking "gaunt and grim," so he might have transformed the night before. At Christmas, however, it is stated that Remus Lupin comes over to the Burrow and even uses Bill's bedroom. 24 December, 1996, is the exact date of a full moon and, since Lupin was already living with the werewolves, there was little chance he could get the seven days worth of doses of Wolfsbane Potion required to make him harmless. Therefore, on that night he would have been a dangerous transformed werewolf.

Chapter 1: The Other Minister

• Cornelius Fudge meets with the Muggle Prime Minister in the first chapter. At the time that this chapter is set, the real life UK Prime Minister was John Major, but the book has some inconsistencies with this. Firstly, there are references to the election, but Major wasn't elected when he first assumed office and simply took over following Margaret Thatcher's resignation. Secondly, Fudge refers to the Prime Minister's predecessor as 'he'. Thirdly, he says that the predecessor tried to throw him out the window after the shock of learning about the existence of the Wizarding World from him, but Thatcher would've already heard about it from a previous Minister for Magic and therefore wouldn't have been shocked to meet Fudge, so probably wouldn't have tried to throw him out the window.
  • It is possible that J.K. Rowling was thinking of Tony Blair when writing this chapter, as he was PM at that time, in which case all these references would apply to him. He was elected when he came to power, his predecessor (i.e. Major) was male and Fudge would've been the first Minister for Magic that the predecessor met.
  • It is also possible that this Prime Minister is fictional and not intended to be any real life figure.

Chapter 2: Spinner's End

• Snape tells Bellatrix he had sixteen years worth of information on Dumbledore to give to Voldemort when Voldemort returned in Harry Potter and the Goblet of Fire. However, the time between Voldemort's original downfall and his return was less than fourteen years.

Chapter 5: An Excess of Phlegm

• On page 101 of the earliest printings, and in the original audiobook editions of Harry Potter and the Half-Blood Prince, Ron mentions that Hermione got ten Outstandings and one Exceeds Expectations for Defence Against the Dark Arts, giving her a total of eleven O.W.L.s. However, since she dropped both Divination and Muggle Studies in her third year, she could not possibly have got eleven O.W.L.s since she was only doing ten subjects — Transfiguration, Charms, Herbology, Potions, Defence Against the Dark Arts, History of Magic, Astronomy, Care of Magical Creatures, Arithmancy, and Ancient Runes. This error was corrected in later editions, in which Ron instead says nine Outstandings and one Exceeds Expectations.

Chapter 6: Draco's Detour

• In the British audiobooks, when the Weasleys, Harry and Hermione are in "Weasley's Wizard Wheezes", the narrator says "patented daydream charms" in a voice that might indicate calling, but it is actually a sign on the product box and there are no quotation marks indicated in the print version of the book.

Chapter 7: The Slug Club

• On page 126 in Chapter Seven on some American Editions it says Chapter One.
• Malfoy paralyses Harry and puts his invisibility cloak on him in the hopes that Harry will be sent back to London on the school train before anyone missed him. However, it was established as early as the first book that passengers on the train are typically instructed over the intercom system to leave their luggage and other belongings on board so that the Hogwarts house elves can collect them and bring them to their respective dormitories. So by all accounts, Harry should have quickly discovered long before the train began its return trip.

Chapter 9: The Half-Blood Prince

• At the start of term feast, Dumbledore tells Quidditch hopefuls to put their names down for selection. For the Gryffindor House, at least, there had never been trials before. Katie Bell also warns Harry against just "picking the old faces," but this had automatically been the case for the five years preceding Harry's sixth year. It is likely Wood was happy with the team for three years, and there was no reason to hold a trial with no spots becoming vacant up until he left. There was no need to hold trials in Harry's fourth year. Angelina Johnson held trials in Harry's fifth year, but only for the parts that needed to be filled in; this could mean that Angelina was happy with the remaining players on the team.
  • This may also be a sign of Harry simply bowing to pressure since he could have chosen to allow those that were already on the team to continue playing but instead chose to take Katie's advice.
  • It is also possible that a new team is chosen only if there's a new captain.
  • Lastly, it could be that Katie was referring to the bad players from the year previous, and simply wanted to replace the players whom had weighed down the team.
• Harry is made Gryffindor Quidditch Captain in his 6th year, however Katie Bell who is attending her 7th and final year of Hogwarts is not made Captain. The mistake is that since Angelina took over for Wood when he left school, it is assumed that the next highest grade player would be chosen as a new Captain for the Team. Following that logic, Katie should have been picked instead of Harry, but she did not even consider herself becoming Captain when she says, " "I thought you'd get that, well done," she called over, pointing at the Captain's badge on Harry's chest. "
• In the sixth year's first Potions lesson with Slughorn, where he offers Felix Felicis as a prize, he states that the vial contains "enough for twelve hours' luck." However, when Harry is considering taking it to get the memory from Slughorn, he tells Ron and Hermione that he would only need to take a bit of the potion, "not twenty-four hours' worth." This error, found only in the American version of the book, is corrected in later editions.
• It says, "Draco had a look on his face similar to the time Hermione had punched him", but in the novel Harry Potter and the Prisoner of Azkaban, Hermione slaps him. This is true in the film adaptation, though, so J.K. Rowling may had mixed up the events of the films and the books.

Chapter 10: The House of Gaunt

• On page 196 (American Edition), Harry is mentioned going to Dumbledore's office for his private lesson on the 7th floor of Hogwarts. When it is shown that Dumbledore's office is on the 3rd floor of Hogwarts in the 2nd book (Chamber of Secrets/Chapter 12: The Polyjuice Potion), when Harry is taken there by Professor McGonagall.

Chapter 11: Hermione's Helping Hand

• First year students show up for the Gryffindor Quidditch team tryouts, despite the fact that, according to Hogwarts rules, first-years are not allowed to try out for house teams.
  • However, as many other non-Quidditch playing students as well as students from other houses attended the tryouts to be near Harry, it is possible that these first-years followed their example. It is also likely that Harry chose to allow first-years to participate to gauge if they had special talent regardless of age, as Harry himself was exempted from the first-year rule and allowed to join the team due to his exceptional talents as Seeker.

Chapter 13: The Secret Riddle

• It says, "... Dumbledore entered the room... It was a small bare room with nothing in it except an old wardrobe and an iron bedstead." A couple paragraphs later, "Dumbledore drew up the hard wooden chair beside Riddle, so that the pair of them looked rather like a hospital patient and visitor."
  • This may have been a pun, since with Dumbledore especially, the term "draw up a chair" is used literally several times when Dumbledore magically conjures a chair by drawing it. This may have been a covert way of implying this, especially considering Riddle may have missed this action by Dumbledore.

Chapter 16: A Very Frosty Christmas

• On page 342 of the American version, there is a punctuation error when Molly Weasley says "Have a little purkey, or some tooding...I mean-" to Rufus Scrimgeour. There are no quotation marks in front of the "have" in the statement. This mistake is corrected in later printings.

Chapter 19: Elf Tails

• On page 415 of the American edition, it says "...McLaggen took a ferocious swipe at the Bludger and missed it." In the original edition "missed" was mistakenly printed as "mishit". This was corrected in later editions.

Chapter 22: After the Burial

• Harry sees Dean, Neville, and Seamus in the common room just before he takes Felix Felicis. But as he is leaving Gryffindor tower a few minutes later, Dean and Ginny are entering through the portrait hole.

Chapter 23: Horcruxes

• Dumbledore says that Voldemort didn't want to wear Gaunt's ring after turning it into a Horcrux, but Harry saw Voldemort wear the ring in Slughorn's memory. Pursuant to Morfin's memory and Dumbledore's explanation, the Riddles were killed right after Voldemort met with Morfin and stole the ring. There would not have been enough time for Voldemort to steal the ring, return to Hogwarts, and then kill the Riddles and make the ring into a Horcrux.
  • However, it is possible that a Horcrux does not need to be made immediately following a person's death; for instance, Riddle could have killed his parents, stolen the ring, worn the ring at school and then, sometime later, used the damage inflicted on his soul upon murdering his parents to make the ring into a Horcrux, at which point he would have stopped wearing it.

Chapter 30: The White Tomb

• Rufus Scrimgeour tells Harry that the Ministry believes he was with Dumbledore when he left the school since there were two brooms on the Astronomy Tower and that "someone Stupefied a Death Eater on top of the Tower after Dumbledore died." However, while Harry did incapacitate said Death Eater, Harry used Petrificus Totalus (the Full Body-Bind Curse) and not Stupefy (the Stunning Spell).

Harry Potter and the Deathly Hallows

Chapter 1: The Dark Lord Ascending

• With the death of Albus Dumbledore, Severus Snape should have become a secret-keeper for the location of 12 Grimmauld Place, and thus could have revealed that information to Voldemort. Perhaps Moody's Tongue-Tying Curse was keeping him from disclosing the information, but if that were the case, the casters of the Fidelius Charm could use the curse more often to prevent the sort of treachery that lead to Lily and James Potters' deaths.
  • More likely he did become a secret-keeper, but hid this fact from the Death Eaters due to his true loyalty secretly being to Dumbledore, and since Voldemort did not know Dumbledore was the Secret Keeper, he wouldn't suspect Snape. It is also possible that Snape indeed told Voldemort, but the latter believed it was worthless to go there since the Order would have changed their headquarters.

Chapter 2: In Memoriam

• It is said that Harry cannot use magic due to not coming of age for another four days. In chapter six, days have passed since the Battle over Little Whinging, but Harry states the Trace will break in four days.

Chapter 4: Seven Potters

• As Harry is awaiting the Order, he reminisces about the few times as a boy he was left alone at Privet Drive as the Dursleys went out for fun, mentioning how he would often play on Dudley's computer and sneak tasty treats from the fridge. However, in Harry Potter and the Philosopher's Stone, it is made clear that the Dursleys would never do anything of the sort, fearful that they would come back to find the house in ruins, instead opting to leave him with a babysitter (preferably Arabella Figg). However, it is possible that he was referring to summer holidays after he had found out he was a wizard, such as in the summer of 1994, when the Dursleys had significantly let up on their abuse of Harry out of fear of retaliation from Sirius. However, by that point, he would likely have had no interest in Muggle entertainment such as television or video games.
• Right before the Battle of the Seven Potters, Moody explains that the Ministry has restricted the use of Portkeys, Floo Network, or Apparition within the Dursley's house, which is why they had to resort to the elaborate "Seven Potters" ruse to get Harry to safety. However, this restriction only applied to the Dursley's home. They could have just placed a Portkey one foot outside the Dursley's lawn and had Harry jump to touch it, or have Harry grab Moody's arm and jump off the lawn at the count of three before undergoing side-along Apparition. Even if they absolutely had to use the "Seven Potters" ruse initially, the fourteen of them could have just disapparated - side-along or otherwise - the minute they took flight. However, they were still unable to use magic around Harry due to the Trace, even if we disregard this inconsistency.
• Couldn't Harry and Moody have simply walked together under the Invisibility Cloak a safe distance away from the Dursley's home (such as Mrs Figg's front yard) before undergoing side-along apparition?

Chapter 5: Fallen Warrior

• Harry says 'What d'you mean? Isn't anyone else back?' but the first apostrophe is missing

Chapter 13: The Muggle-Born Registration Commission

• Harry and Hermione call each other by their real names while freeing the Muggle-Borns awaiting trial, rather than those of the people they are impersonating, which is sure to blow their cover.

Chapter 14: The Thief

• Hermione is afraid to return to 12 Grimmauld Place for fear that she had inadvertently given the location to Yaxley. Harry theorises that Yaxley is also bringing other Death Eaters into the place. However, Yaxley should have been unable to do so, as only a secret-keeper can reveal a location hidden by the Fidelius Charm, and Yaxley would not have become a secret-keeper simply by learning a hidden location from another secret-keeper. He would only become a secret-keeper if the secret-keeper who reveals the secret to him (in this case, Hermione) actually dies. It is also a part of Fidelius Charm lore that a secret-keeper cannot be coerced into revealing the protected information; it must be divulged willingly. Therefore, Yaxley should not have been able to learn the secret simply by grabbing onto Hermione and not letting go, as this would not have been voluntary on Hermione's part.
  • However, this could just be Harry and Hermione's speculation based on their limited knowledge on the Fidelius Charm. Although Hermione should probably have read about it before, since she always loved to read.

Chapter 15: The Goblin's Revenge

• Ted Tonks uses Summoning Charm on a fish in the river by sayin 'Accio salmon' and it works. However it is said in the Book of Spells and Rowling's Official Site that 'Accio only works for inanimate objects'. A possible explanation is that the summoning charm merely causes irreparable harm to living things, such as turning their organs inside out, and since Ted and his friends were just planning on eating the salmon anyway, this wasn't a concern for him.

Chapter 20: Xenophilius Lovegood

• Ron explains that Voldemort had placed a Taboo on his name so that if anyone said it he would be able to find that person, and explains that was how the Death Eaters had found them on Tottenham Court Road — Hermione used the name once, while they were sitting in the cafe. However, the trio used Voldemort's name several times while they stayed at 12 Grimmauld Place, and the Death Eaters did not manage to find them there until Hermione accidentally brought one back with them, after Disapparating from the Ministry of Magic, although one or two strangers did appear near Grimmauld Place before with a dozen on September 1st. The charms placed on 12 Grimmauld Place which make the location impossible to enter unless invited but the jinx placed on Voldemort's name is specifically said to "break protective enchantments." However, it is highly likely that it may not be able to break the Fidelius Charm, which is notoriously strong.
• When Harry, Ron, and Hermione are at the front door of Lovegood house, Hermione says to Harry, "You better take off the Invisibility Cloak, Harry, it's you Mr Lovegood wants to help," and he handed her his Cloak to place in the beaded bag, but after the Death Eaters arrive Hermione says, "Harry give me the Invisibility Cloak, Ron, you're going to put it on." 

Chapter 23: Malfoy Manor

• Narcissa says that Draco "is home for his Easter holidays." In the next chapter, the sun is described as rising at Shell Cottage in Cornwall, but shortly after this, Harry sees into Voldemort's mind at Hogsmeade, where it is "still dark, because it was so much farther north." However (in the absence of a significant longitudinal difference, as in this case), this sort of thing is only true between the Autumnal and Vernal Equinoxes; Easter occurs after the Vernal Equinox (e.g. on 12 April in 1998), in the other half of the year when sunrise is earlier the further north one goes, thus it should not have been dark at Hogwarts when Harry saw into Voldemort's mind.

Chapter 25: Shell Cottage

• Lupin says that Bill is the Cottage's Secret Keeper, yet Ron was able to tell Dobby about where the cottage was when escaping from Malfoy Manor. However, this is most likely because Ron was aware of the cottage's existence prior to the Fidelius Charm being placed on it, and thus was free to divulge the information on its whereabouts. However according to this logic, Bellatrix Lestrange should be able to tell Voldemort about 12 Grimmauld Place.
  • However, it is possible that the Fidelius Charm does not work on elves, since it is shown multiple times in the books that elf magic works differently with wizard magic.
  • It is also possible that Dobby merely Apparated right outside Shell Cottage for the Secret Keeper, Bill Weasley to lead them in.

Chapter 27: The Final Hiding Place

• Harry drips dittany through the singed hole in his jeans to the angry burn beneath, but he has just got changed, so he shouldn't be wearing his singed jeans anymore. Not much later in this chapter, Harry returns from an excursion into Voldemort's mind, and is "vaguely surprised" that he is "still wet to his skin", which he should not be since he had got changed into dry robes earlier. Harry may have been so affected by this excursion that he woke up in a cold sweat, however this is unlikely, since Harry has had a lot of experience seeing Voldemort's thoughts by this point, and because the statement implies that Harry's clothing is still soaked.
• When Harry is viewing Snape's memories, he witnesses a scene on Platform 9¾ between his mother and Aunt Petunia, in which Petunia tugs her hand out of Lily's grasp. Her hand is then back in Lily's, and she tugs it out again.
  • Lily may have grabbed her hand again against her will.

Chapter 33: The Prince's Tale

• Dumbledore asks Snape to cast a Confundus Charm on Mundungus Fletcher, but since Voldemort took over the Ministry after the chase, Snape shouldn't have been able to enter Hogwarts and go to the Headmaster's Office. Unless Dumbledore showed him a way to enter unnoticed, had allowed him access, or something similar.
  • It is also possible he used the Vanishing Cabinet in Borgin & Burkes to enter the Room of Requirement at night and thus sneak to the Headmaster's Office, or used the same passage through the Room of Requirement that the DA later used.
  • Alternatively, he might have entered at day time and used a Disillusionment Charm in order to render himself almost invisible and spy on his former colleagues in order to find out what the password for the office is.
• Dumbledore tells Snape to give Voldemort the correct date so as to avoid blowing his cover, since Voldemort would expect Snape to know the correct date given Snape's position as an Order insider. However, by this point, Snape should have been completely exiled from the Order of the Phoenix, meaning he should not be in any position to be privy to the Order's plan.

Chapter 36: The Flaw in the Plan

• Harry sees Charlie Weasley overtaking Horace Slughorn and in the next page Voldemort is seen duelling McGonagall, Slughorn, and Kingsley; however, Slughorn could have caught up again.

Harry Potter and the Cursed Child

Part 1

Act 1

• Scene One and Scene Two take place in the Epilogue: Nineteen Years Later of Harry Potter and the Deathly Hallows. However, there are a few modifications. In Harry Potter and the Cursed Child (Special Rehearsal Edition), the whole Potter family run into the barrier together. In the book, James leaves before the rest of his family. Some lines in the book are not said by the same characters. In the play it's Harry who says "James, give it a rest" while in the book it's Ginny.
  • Albus explains why he doesn't want to be in Slytherin, stating "Slytherin is the House of the snake, of Dark Magic... it’s not a House of brave wizards".

Act 2

• When Eloise Mintumble time-travelled and changed things, it was noticed by other witches and wizards from the original timeline who went to retrieve her without seemingly time-travelling themselves. When Albus Potter and Scorpius Malfoy time-travelled and changed things, no one from the original timeline knew they could retrieve them. They never mention being able to retrieve them in the same way Eloise was retrieved.
• When Eloise was retrieved, her body aged the five centuries it had to travel through, and it created paradoxes such as Tuesday lasting two and a half days and Thursday going by in only four hours. When Albus and Scorpius time-travel, the only real consequences was that things had changed and Albus' arm being injured as if it broke twenty years ago and 'allowed to set in the 'most contrary of directions'. There are no paradoxes.

Part 2

Act 4

• In the play, Polyjuice Potion seems faster to make. In Act 4, Scene 10, Albus proposes that they use this potion to turn into Voldemort because he thinks Bathilda Bagshot may have all the ingredients, and Ron only contradicts him with the argument that they don’t have a bit of Voldemort, just like as though the one month of preparation was not an issue when they only have a few hours ahead of them.
  • Both may have assumed that either they could use the Turner again to give themselves time to make the potion or Bathilda would have a potion ready for their use.
• Harry only had the ability to speak Parseltongue because he was a Horcrux. He never knew how to speak it himself. It only happened because he had a piece of Voldemort's soul residing in him. Rowling stated this to be correct in an interview when she confirmed that Harry "lost the ability and was very glad" when Voldemort destroyed that part of his soul. However, in the play, he speaks it anyway as though he had never lost the ability.

Rowling's Companion Writings

• Quidditch Through the Ages
  • A discrepancy is that although Harry had the book in his first year (1991-1992), there is an event listed that occurred in 1994. It is, however, possible, that the "real" edition was updated.
  • In chapter 4, a witch named Modesty Rabnott summons a Golden Snidget by using Summoning Charm, but living creatures can't be summoned by this spell.
  • In chapter 7, it says that the first Quidditch World Cup was held in 1473. If the championship is held every four years, this conflicts with the statement in Goblet of Fire that the 1994 championship was the 422nd. If Quidditch Through the Ages is right, the 422nd Quidditch World Cup was actually held in 3161, but if Goblet of Fire is right, the first World Cup was actually held in 306.