Ghost Plots

GHOST PLOTS AND RED HERRINGS JK Rowling defines "ghost plots" as "information" "superfluous to requirements" that "never appeared in the books" or as storylines that were "sacrificed for the bigger story". JK Rowlings assurtion that some ghost plots never made the "final cut" indicates that that they may have appeared in earlier drafts of a book before being removed. If the removal was incomplete, the remnant from a removed ghost plot may appear as a red herring - a term usually reserved for details mascarading as clues or mistaken for clues. For example, Florean Fortescue and his knowledge of wizarding history made an appearance in the books before JK Rowling decided against using him as a means for Harry to discover information about the Hallows and Horcruxes. 

JK Rowling's assertion that she sometimes included a "throw-away detail" from a ghost plot in the books indicates that ghost plots do not neccessarily fit neatly into the canon versus non-canon dichotomy. One of these "throw-away details" was Harry overhearing Dean Thomas explain that he did not know whether his biological father was a wizard or not because he left when Dean was a baby. The ghost plot that was cut would have had Dean discovering that his biological father was a wizard and why he left. Thus, it made sense for JK Rowling to include a remnant from a known ghost plot in the book. The part of the ghost plot where Dean discovers the truth about his father is not canon because, according to the conversation in DH 15, Dean doesn't discover the truth about his father. Not all known ghost plots were removed because they were peripheral to the main story. Arthur Weasley's death was removed from OOTP because JKR decided she wanted one of the few good fathers in the books to live. The removal of this ghost plot did not shorten the story since the circumstances which may have caused Arthur's death - a bite from Nagini while he was hidden in the Hall of Prophecy at the Ministry remained intact. The need to cover up the circumstances under which Arthur was bitten would exist whether he lived or died, so would Sirius Black's explanation to the Weasley twins as to why they could not see their father, who might be dying, until after the hospital contacted their mother.

Removing Arthur's death plot did mean that, not only did any reference to Arthur being dead needed to be scrubbed from the rest of the series, but that Arthur also had to make at least an appearance in other books - meaning that he had to be written in and given things to do or say. It is not know whether JK Rowling invented a part for Arthur in subsequent books from scratch or whether she borrowed bits and pieces of storyline for him originally assigned to other characters.

Sometimes JK Rowling took questions concerning the books either before a particular ghost plot had been removed or while momentarily forgetting that it had been removed. Subsequently, she admitted on Pottermore that when she said something in an interview that did not match the book, it was due to a ghost plot.

Known Ghost Plots

 * Arthur Weasley's death
 * Dean Thomas finding out the truth about Dean Thomas's Father
 * Mafalda, the nosy Weasley cousin
 * Hermione Granger's sister, a younger muggle sibling