Trivia: In the end credits (approx 2:14:11), where the Motion Control Camera crew are listed, there are two pairs of shoe shapes showing in the lower left hand corner tower. Borrowing a quote from the film, "I swear [they] are up to no good.", because the shoes are positioned in such a way that it gives the appearance that they are engaged in a particularly adult diversion.
Trivia: 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 one of the houses represented by a snake (Slytherin) and one represented by an eagle (Ravenclaw) respectively.
Trivia: When 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.
Trivia: The name of the driver of the Knight Bus is Ernie Prang. 'Prang' is an uncommonly used British slang word which means to wreck or crash an automobile.
Trivia: Michael Gambon was cast as Dumbledore after Richard Harris died. He's known for fooling around such as ad-libbing upstage or moving a pencil a couple of inches across a table after a director has set up a shot. "He's a clown," said Matthew Warchus who directed him in 3 other films. "He has the gravitas, and sadness, and extraordinary comic nature of a great clown. And he's also great fun and remarkably easy to work with."
Trivia: Alfonso Cuaron so desperately wanted practical effects in the film that he trained a kickboxer and a dancer for seven months in werewolf suits for the scenes with Lupin. When he realised that the rocky terrain would not be suitable for the stilts inside the werewolf suits, he relented and had them computer generated. Oddly enough, he also directed Gravity, which for about 80% of the film is CGI.