1. Filming for Chamber of Secrets started just three days after filming for Philosopher's Stone finished.
3. Chamber of Secrets was Daniel Radcliffe's favourite book of the series.
6. And the drawings on the kitchen wall were made by children from a local school.
7. Mark Williams, who played Arthur Weasley, said that filming in the afternoons was always fun because Daniel Radcliffe and Rupert Grint often got the giggles.
8. Bonnie Wright, who played Ginny Weasley, was allowed to bring one of her best friends to the film set to be an extra.
9. During filming, Rupert Grint drew an unflattering picture of Alan Rickman to make his peers laugh. When Rickman saw it, he made Grint sign it and then confiscated it. He still has it.
10. When Emma Watson hugged Radcliffe in the film's final scene, she was so embarrassed by the concept of hugging a boy that she let go too quickly. Producers had to freeze the screen for one second so the hug appeared longer.
11. The reason she shook Grint's hand was that she was too embarrassed to hug him too.
12. When asked whose body she would inhabit if she could drink Polyjuice potion IRL, Watson says she would have become Jennifer Aniston so she could see if Brad Pitt was that good-looking close up.
13. Radcliffe says he would become Spider-Man so he could kiss Kirsten Dunst.
14. And Grint said he would have become a cartoon.
15. During filming, Watson's hamster Millie died. The props department built Millie a coffin with a velvet lining and a silver nameplate on the front, and hosted a funeral for her.
16. At one point during filming, there was an outbreak of head lice. Everyone had to be checked.
17. Jason Isaacs, who played Lucius Malfoy, came up with the idea of him having long hair.
18. Before he met Tom Felton, Isaac thought he would be an "unpleasant kid". But instead, he found Felton "thoroughly charming".
19. He also said that Felton was "a little heart throb on set".
20. Both Radcliffe's and Grint's voices broke during filming Chamber of Secrets.
21. And it was reported that a voice double had to be used for some of Radcliffe's lines toward the end of filming.
22. In Philosopher's Stone, Martin Bayfield was Robbie Coltrane's body double. In Chamber of Secrets, he also played young Hagrid in Tom Riddle's memory scene.
23. Throughout filming, Dobby was just an orange ball on a stick. His features were added in digitally.
25. A trench had to be built around the Quidditch pitch especially for the scene in which Harry is chased around the pitch by a bludger.
26. Draco Malfoy's line "I didn't know you could read" to Goyle was improvised by Felton.
27. Similarly, Lucius Malfoy's line "Let us hope Mr Potter will always be around the save the day" was improvised by Jason Isaac.
28. And Daniel Radcliffe improvised the reply "Don't worry; I will be."
29. Matthew Lewis, who plays Neville Longbottom, says that his favourite line from all of the films was "Why is it always me?" Neville says this line when the Cornish pixies hang him from the classroom light.
30. Hugh Grant was up for the role of Gilderoy Lockhart before Kenneth Branagh was cast.
31. Parseltongue was invented by the linguistics department of Cambridge University.
34. The slugs that Ron throws up were chocolate-, peppermint-, lemon-, and orange-flavoured.
35. Most of the stone steps inside Hogwarts were made of wood.
37. And finally, Fawkes was so realistic-looking that Richard Harris thought he was a real bird wearing a Phoenix costume.