Continuity mistake: When running from Aragog, there is one quick shot of the back of the Anglea and the hole that was punched into the back window by the Whomping Willow has vanished to return only a few seconds later.
Harry Potter and the Chamber of Secrets (2002)
301 mistakes - chronological order
Directed by: Chris Columbus
Starring: Maggie Smith, Alan Rickman, Kenneth Branagh, Richard Harris, Daniel Radcliffe, Jason Isaacs, Emma Watson, Robbie Coltrane, Tom Felton, Rupert Grint, Richard Griffiths
Genres: Adventure, Family, Fantasy, Harry Potter, Mystery
Uncle Vernon: And Dudley, you will be?
Dudley Dursley: I'll be waiting to open the door.
Uncle Vernon: Excellent. And you?
Harry: I'll be in my bedroom, making no noise and pretending that I don't exist.
Trivia: When Hagrid is welcomed back to Hogwarts and everyone stands up and applauds, Vincent Crabbe also stands up and starts to applaud as well. This wasn't in the script and Tom Felton, staying in character, quickly grabbed Jamie and pulled him back down.
Question: Is this true that line "I didn't know you could read" was improvised by Tom Felton, who forgot his original line?
Answer: Yes in the same way Daniel Radcliffe improvised his line about always being around when talking to Lucius at the end.
Actually, Jason Isaacs said that, and he and Daniel didn't forget their lines but did it intentionally.
Answer: Yes. It's a common occurrence in a lot of movies for actors to forget their original lines so they improvise something to help move the scene along and not break character. Tom did this because he forgot what his original line was.