There are lightbulbs in Honeydukes. [In the books it is stated that electricity doesn't work in the magical world, so lightbulbs in Honeydukes would be an impossibility. However, it is never stated in the movies that electricity doesn't work, so this isn't a mistake, it's a book/movie inconsistency.] Corrected by Blibbetyblip

When Peter Pettigrew is seen on the Marauder's Map, his dot's footprints are displayed as that of a human's even though he is in his rat form. However, during the credits Sirius' dot is shown changing from human footprints to dog pawprints and back again. Either Peter's prints should've shown up as rat prints or Sirius' should have consistently been shown as human prints. [That was just something cute they did for the credits, it isn't meant to be taken as film canon. The Marauder's Map shows what is truly there; Peter Pettigrew is a human whatever shape he may take, so his footprints appear on the map as a human's.] Corrected by Phixius

David Thewlis was originally considered to play Professor Quirrell in "Harry Potter and the Philosopher's Stone." Ironically, Thewlis is friends with Ian Hart, who did play the role. [This is not trivia for this film.]

Platform Nine and Three Quarters is supposed to be a secret platform that only magical people can access. However when Harry, Ron and Hermione have boarded the train and are looking for a cabin we can see out of the window a GNER (Great North-Eastern Railway) train visible on the next platform. The train is most noticeable for its blue colour with a single red stripe running the length of the train. [The Hogwarts Express is very much the same as the Knight Bus that Harry takes to the Leaky Cauldron, in the sense that muggles cannot see it, even when in the same vicinity as other cars. The same principle applies for the train sitting on the platform at the station next to the real trains.] Corrected by Jazetopher

When the Dementors are boarding the train, everything starts to go cold, so much so that the water on the windows starts to freeze, and even more noticeably the water in the bottle completely freezes. Once the Dementors have gone, the windows are completely free from ice and the water in the bottle has melted again. This is not possible in the short space of time that passed. [Neither water nor windows can freeze that fast either. Dementors are magic creatures, and have magical effects on their surroundings.] Corrected by Sereenie

At the Leaky Cauldron a guy picks up a bottle and wraps a rag around it. A second later the bottle is gone. [It's magic. Not a mistake, the bartender was using magic to clean up.] Corrected by scaryterri

When the Hogwarts Express stops and Ron turns to look out the window, Hermione says "Ouch Ron, that was my foot". However, in the next shot, Ron's feet are nowhere near Hermione's. He would have had to have been leaning in order to reach her foot, and he's sitting up pretty straight, too fast for it to change in one shot. [It's pretty dark and Hermione might have mistaken a big shape for Ron.]

When the entire school is banqueting after their arrival, D. Malfoy says: "Potter. Is it true you fainted. I mean you actually fainted?" In the book, he found out because Neville was in the compartment as well, and he told "nearly everyone." But, in the film, only Harry, Hermione, Ron, and Professor Lupin are in the compartment. The three friends wouldn't have told them, and a schoolteacher doesn't go around telling such things to students. So, as Harry himself asked, how did Malfoy find out? [There are large windows on the compartment facing the hallway, which showed considerable traffic previously and in the other movies because the snack cart was located farther up the train. It is reasonable that someone saw what had happened during the time that Harry was unconscious or was alerted to the scene by Harry's screams, that Ron discussed.] Corrected by OneHappyHusky

When Hermione says "I thought I just saw. Never mind" the second time, it is in a much lower tone than when she first said it. [Thats becasue when we hear it, we are listening from the woods. The first time we are listening from her.] Corrected by James Storck

In the scene where Hermione is about to punch Malfoy, the wand Hermione sticks at him is in her right hand. It cuts to the next scene, and Hermione punches Draco with her right hand. You never see her wand switch hands in between. [Hermione would have plenty of time (off-camera) to switch hands.]

The first time Uncle Vernon comes into Harry's bedroom, the light switches off a split second before he flips the switch (seen in slow motion). [This scene looks completely OK at normal speed.] Corrected by tw_stuart

Harry's wand looks completely different to the one in the first two movies. [The director has artistic license to change things the way he sees them. Hogwarts robes, geography, etc. are different in each of the films. Not an error here.]

Harry never notices that the name "Peter Pettigrew" appears on the Marauder's Map, right next to "Ronald Weasley". Way beyond a character mistake, as there's no way that wouldn't be cause for interest. [Ron doesn't appear to have Scabbers with him most of the time and Harry doesn't spend all his time poring over the map so it's entirely possible that he wouldn't catch the two names together. Scabbers then vanishes not long after Harry gets the map (Ron and Hermione argue about it repeatedly), so the names wouldn't appear together any more after that.]

When the Knight Bus slows down before the two double-deckers, you can see them and the other traffic around it slow down noticeably as well. The other vehicles also speed up when the Knight Bus does. [Clearly, the bus is altering the flow of time around it to give it time to make its squeeze. It wouldn't make much sense to slow the Knight bus down only to have all the surrounding traffic slam right into it.]

When Dumbledore is studying the slashes on the portrait of the Fat Lady, you can see, especially well when the light shines on it, that the actual paining is extremely smooth. But a real paining would have at least some trace of paint brush strokes. [A real painting probably would. An enchanted painting in a school of witchcraft and wizardry might not.]

When Arthur Weasley takes Harry aside in The Leaky Cauldron to warn him about Sirius Black, he says, "13 years ago, when you stopped.... You-Know-Who...Black lost everything." Harry is 13 yrs. old in Prisoner of Azkaban and was a 1 yr. old when he stopped Voldemort. Hence, Harry stopped Voldemort 12 yrs. ago, and not 13! Harry turns 11 just before school starts in Philosopher's Stone, turns 12 before school in Chamber of Secrets and turns 13 yrs. old before school in Prisoner of Azkaban. Just an aside, the last digit of Harry's age always coincides with Harry's year at Hogwarts. So, he's 13 in his 3rd year at Hogwarts, which is entitled Prisoner of Azkaban. [This is a case of bad math on mr. Weasley's side, and as such, not a movie mistake. Either he mixes up the dates, or he tries to subtract the year Voldemort was defeated from the present year, and comes up wrong. Either way, character mistake.] Corrected by Twotall

When Harry and Hermione travel back in time to save Sirius, there is a continual ticking sound heard right through until they catch up with themselves in the hospital. [Yes, but since everyone can hear it clearly for themselves while watching the movie, it's not really trivia.] Corrected by Twotall

On the Hogwarts Express, when Ron says, "Let me get this straight," he glances into the camera. [When Mr. Weasley originally explained this to Harry, he took him away from everyone else. This tells us that he didn't want anyone else to know, so Ron was also checking that there was nobody outside the compartment who could overhear their conversation - he is looking past the camera, as if the camera is not there. ]

When Harry and Hermione are back in time and watching Dumbledore knock on Hagrid's door, Harry glances into the camera briefly. [Perhaps the character briefly looked in that direction by chance. For the purposes of the movie we are assuming that the camera isn't there, so anyone looking at the camera is simply looking at something in that direction.]

When Neville has the Boggart explained to him, he switches positions between shots. [Because of the camera angles there is NO way to tell if he change position whatsoever. He is standing perfectly still.] Corrected by Mortug