Curiosities

Daniel Radcliffe broke more than 80 wands while recording. The actor liked to use them as drumsticks during the recording of the film.
Daniel Radcliffe used more than 160 glasses during the recording.
The actress who played Moaning Myrtle was, at the time of filming "Harry Potter and the Chamber of Secrets", 37 years old. She is the oldest actress who acted in the role of a Hogwarts student.

Only Alan Rickman, Professor Snape's actor, knew his character's fate before the release of "Harry Potter and the Deathly Hallows", as JK said so.
Rupert Grint dressed up as his drama teacher and rapped Ron Weasley at his audition.
During the shooting of the kiss between Harry's version of horcrux and Hermione in the end, Rupert Grint was removed from the set for laughing too much.
Tom Felton auditioned for the roles of Harry Potter and Ron Weasley, but was soon chosen to act as Draco Malfoy.

During the filming of "Harry Potter and the Prisoner of Azkaban", Tom Felton's Hogwarts clothing pockets were sewn together because he kept trying to bring hidden food to the set.
Robbie Coltrane, the Hagrid actor in the films, had a mini fan stuck in his beard.
In order for the 3 actors to be familiar with the films, director Alfonso Cuaron made each one write an essay about their characters. Truly, Emma Watson wrote 16 pages, Daniel Radcliffe wrote only one and Rupert Grint never delivered his essay.
Maggie Smith, who played Professor McGonagall, battled breast cancer during the recording of the last film in the saga. She didn't stop acting because she didn't want to disappoint fans.