Continuity mistake: On the train, when Ron introduces Harry to Scabbers there are two Jelly Slugs lying on Ron's leg - one red-green and one yellowish-brown, but when Ron casts the spell on Scabbers both Jelly Slugs are red-green, and then it switches back again. (00:36:40)
Continuity mistake: When Professor McGonnagall is talking to the children before their sorting, you can tell when the camera is on her that the lighting is candle-like (note the flicker). When the camera cuts to the children, there is no flicker (check out Hermione). (00:39:50)
Continuity mistake: While the first years are waiting at the top of the stairs just before being lead into the Great Hall for the first time, Ron's robes switch from being fully opened, to closed, then back again. (00:40:00)
Continuity mistake: When Malfoy first talks, the window behind him is bright blue. He says "it's true then, what they are saying on the train, Harry Potter has come to Hogwarts." Everyone says "Harry Potter" and when it cuts back to Malfoy, the window is much much darker. Both a mistake in terms of continuity between windows, and also a mistake because we'd seen everyone turn up in total darkness earlier, so the window shouldn't have been lit in the first place. (00:40:30)
Continuity mistake: Malfoy has one tooth that is notably crooked. If you watch carefully, you'll see that it changes sides throughout the film. (00:40:55 - 01:43:50)
Continuity mistake: In the scene where the pupils are waiting on the stairs before being sorted into their houses, Malfoy speaks to Harry and is clearly at the top of the stairs. However as the pupils go into the dining room, Malfoy is nowhere to be seen in at least the first 30 pupils. (00:41:15)
Continuity mistake: In the scene where the new students are walking to their rooms, there seems to be a whole lot more new students then there was in the sorting hat ceremony. (00:41:40 - 00:48:05)
Continuity mistake: When the first years are first led into the Great Hall, in the shot facing the teacher's table, the twins sit to Wood's left at the end of Gryffindor's table. However, in the next shot facing the first years, the twins sit on Wood's right. (00:41:55)
Continuity mistake: In the scene following Harry's sorting, Hermione has changed sides at the Gryffindor table. (00:43:00)
Continuity mistake: At the start of term feast, after Harry is sorted into Gryffindor, he sits down on the right side of the table next to Ron. When the feast appears, Harry is on the other side of the table, next to Hermione. (00:46:05)
Suggested correction: This is not a mistake. In the first shot, Harry was just sorted into Gryffindor and there were still quite a few students waiting to be sorted. By the time of the second shot, all the students were sorted and the feast started. Therefore, at least a few minutes have passed and Harry had plenty of time to switch sides of the table. Doesn't make much sense why he did that, I agree, but still plenty of time to do it.
I agree, but it's not about how there's plenty of time to do it. Like you said before, there's no reason for Harry to change position. Therefore, it counts as a mistake.
Continuity mistake: When Percy leads the group of first years back to the Gryffindor dormitories for the first time, at the stairs he says, "Keep up please and follow me. Quickly now, come on." In this wide shot Harry and Ron run up the stairs first and Hermione is at least six people behind them. Yet, in the next close-up she is with them at the front, right behind Percy. (00:48:25)
Continuity mistake: When we see Ron and Harry running into the transfiguration class, Malfoy and Crabbe can be seen working. When it shows a close-up of Malfoy, both Malfoy and Crabbe have changed body position. (00:48:30)
Continuity mistake: On his first night in the castle, Harry is sat on a window ledge with Hedwig. In this shot, his feet go from resting on their sides and crossed at the ankles to flat and uncrossed. (00:48:50)
Continuity mistake: When Snape enters the classroom during the first Potions class, there is a lit candle and an hourglass on the desk directly behind him. But in the following shots the candle and hourglass change positions and move farther away. (00:49:20)
Continuity mistake: When the three children get past Fluffy because the harp is playing, as Fluffy wakes he dribbles on Ron's shoulder. However, when they fall down into the Devil's Snare, his shirt is completely dry. (00:51:16)
Continuity mistake: When Harry is in the potions class he is caught writing notes down, we see his neat writing in close up ... but when the camera angle changes we can see that the writing has changed in size to very large letters and quite messy writing. (00:52:10)
Continuity mistake: After Seamus' disaster with the rum spell, the mail arrives. Ron catches his mail, then holds the Daily Prophet in his right hand and the letters in his left. Yet in the next close-up he holds the Daily Prophet in his left hand and the letters in his right. (00:54:05)
Continuity mistake: When Neville first takes off during the 1st flying lesson, Ron covers his face with his right hand. When the shot changes, his hand is no longer over his face. (00:54:20)
Continuity mistake: When Madame Hooch approaches and then welcomes the class to their first flying lesson, the angle at which their shadows are cast changes dramatically in consecutive shots throughout this scene; and in some shots there are no shadows. (00:55:00)
Continuity mistake: In the overhead wide shot, before Madame Hooch says, "Good afternoon, class," as she approaches, each student stands directly behind the bristles of their broomsticks, yet in the next shot as the camera pans their feet, they stand between the bristles of their broom and the neighboring broom. (00:55:00)
