Cookie and I thought this up. She's the Doctor, and I am whatever characters are unclaimed.
You really don't need to know the slightest thing about Doctor Who for this.
Premise thingy: The 10th Doctor regenerates into an 11-year-old version of the 11th Doctor, and goes to Hogwarts, not knowing he looks 11 (though he completely acts that way). He gets sorted into Hufflepuff.
Canon claim:
River Song: (first year Slytherin)
Amy Pond: (third year Slytherin)
Rory Williams: (third year Hufflepuff)
Martha Jones: (4th year Ravenclaw)
Clara Oswald: (second year Slytherin)
OC form
Name:
Age:
Year:
House:
S & S:
Wand:
Patronus:
Personality:
Appearance: