Peter Pettigrew's Animagus form is Ron's rat, Scabbers. Timothy Spall previously voiced Nick the rat in "Chicken Run."

When the Dementor enters the carriage, you can hear a sort of underwater bubbling sound. This is a tribute to the fact that director Alfonso Cuaron originally wanted the Dementors to be puppets filmed underwater; this was changed due to the difficulty.

It has been claimed that director Alfonso Cuaron, being a Mexican, included at some point in the movie the image of an eagle devouring a snake, which is the national symbol of Mexico. This is seen on the statues by the fountain; however, it could also be passed off as a Hogwarts logo, with two of the houses represented by a snake (Slytherin) and an eagle (Ravenclaw) respectively.

At the end where Dumbledore has just said to Harry and Hermione "Did what?" as he walks away he is humming to the tune of 'The Mexican Hat Dance',which is a tribute to director Alfonso Cuaron, who is Mexican.

During Hagrid's Care of Magical Creatures lesson, stationary figures and an elaborate animatronic figure of Buckbeak were used as reference points for both Harry and the class, for many of the shots. The CGI of Buckbeak was added in post production. (Special Features, Disc 2)

In the scene where Harry is given the Maruader's Map by the Weasley twins, the name 'Moony' is misspelt on the map as 'Mooney'. Not a movie mistake, as it's a book discrepancy, but worth noting for trivia reasons - one of the visual effects supervisors is named Karl Mooney, so the spelling was probably deliberately altered for an in-reference.

The name of the driver of the Knight Bus is Ernie Prang. 'Prang' is a uncommonly used slang word used in Britain which means to wreck or crash an automobile.

Harry's godfather is called Sirius Black; Sirius is a star also known as the Dog Star, so his name loosely translates to Black Dog, his Animagus form.