Duke Humfrey’s Library
To film scenes in the restricted section of Hogwarts’ library, the real-life Duke Humfrey’s Library at Oxford’s Boldleian Library allowed production to take place on its premises. They were even allowed to used a flame in a lantern while filming.
Pronouncing Hermione
J.K. Rowling was constantly asked about how to pronounce Hermione’s name, so she decided to add a scene in Harry Potter and the Goblet of Fire that finally explained it. In the book, the character of Viktor Krum directly asks her how to pronounce her name, and though he struggles, the readers finally got a straight answer about it.