Some Harry Potter trivia for you here. When J.K. Rowling got the layout of King’s Cross wrong in the first book, the London train station had to be knocked down and rebuilt, so that it matched her description.
The prop they used for the Sorting Hat reportedly became infested with head lice. Subsequently, Emma Watson (Hermione) had to shave off all of her hair and wear a wig for the remainder of production. As did Robbie Coltrane (Hagrid), who tried the hat on for a laugh.