Continuity mistake: When Hermione says, "Awful things happen to Wizards who meddle with time, we can't be seen," in the shot facing her she places her right elbow up on the pumpkin. In the next shot facing Harry her arm is down on her lap, yet in the next shot facing Hermione her arm is up again. (01:50:55)
Continuity mistake: When Harry is facing the Boggart shaped as a clown, as Lupin says "Wonderful, wonderful" in the background, we can see Hermione standing right next to another girl behind Harry. But when it cuts to a wide shot from beside them we see Harry standing and we see Hermione standing behind him, but the girl next to her is nowhere in sight. (00:42:10)
Continuity mistake: As Harry quickly flies off on his Firebolt, in the wide shot when he rounds the fountain, Percy, Ron and Hermione stand in front of Fred, George and Neville. However, in the next back shot Fred, George and Neville stand in front of Percy. (02:09:20)
Continuity mistake: When Trelawney looks in Potter's cup she is frightened and throws the cup on the table. We can see it landing with its handle inwards on the table. When it cuts the handle points outwards on the table. (00:29:30)
Continuity mistake: When Trelawney is done looking in Neville's cup and puts it down, you see Neville putting his hands on the table. When it cuts his hands aren't on the table. (00:28:55)
Continuity mistake: When they're having their first Defence Against the Dark Arts lesson and Harry is facing the boggart, Lupin jumps in front of Harry because he thought it would turn into Voldemort, as he later states in the movie. But the boggart had already turned into a Dementor before Lupin makes a move. (00:42:20)
Continuity mistake: At Shrieking Shack when Lupin says "You sold James and Lilly to Voldemort, didn't you?" to Pettigrew, you see Pettigrew holding onto the piano with his left hand. Next shot he isn't holding onto it. (01:32:00)
Continuity mistake: When Aunt Marge flies off, she starts pulling the tablecloth and some food stays on the table but in each of the following shots where there's a view from the side, the table is clean. (00:04:55)
Continuity mistake: When Lupin and Potter enters the classroom after Lupin got the Marauders Map from Snape, Lupin says "But quite frankly, I am astounded that you didn't hand it in." The way he holds the map change in the next shot. (01:14:35)
Continuity mistake: As Potter walks into the Knight Bus you see Stan lifting Potter's trunk inside. When it cuts, the way Stan comes in with the trunk changes. (00:08:45)
Continuity mistake: When Harry collapses next to Sirius after the Dementors have been repelled, the ground where his head lands is covered in fairly small stones. In the following overhead shot of Harry and Sirius, there are some much larger rocks next to his head, and a patch of dirt with no stones is visible to Harry's left, where stones were before. (01:41:00)
Continuity mistake: During Hagrid's class, Vincent Crabe has his shirt outside his pants. He puts his things on the wall and when Draco and Harry are talking, his shirt is now half tucked into his pants. He didn't have the time to do that. (00:31:20)
Continuity mistake: During Hagrid's lesson, when Harry walks towards Buckbeak as Hagrid explains to Harry that he needs to wait for Buckbeak to bow back, etc., in the next shot a boy on the left of the screen drops his cloak to the ground. In the next shot of the students, the boy has it on his arm again, but in the next shot as Harry bows, it's on the ground once again. (00:34:10)
Continuity mistake: When Hagrid cries out, "Buckbeak's been sentenced to death!" in the close-up, Harry Ron and Hermione are visible at the shoreline behind him. However, in the next overhead shot Ron and Hermione are much closer to Harry along the shore. (01:12:50)
Continuity mistake: When Vernon says, "You've nowhere to go," to Potter, you see Vernon grab the banister. When it cuts, the way he holds the banister changes. (00:06:30)
Continuity mistake: When Trelawny says "Look at the cup, tell me what you see" to Ron, the way Ron holds the cup changes between shots. (00:29:10)
Continuity mistake: The second time Harry conjures the patronus charm to save Sirius and the other Harry from the dementors, Hermione is standing next to the tree behind him. The first time he uses it, his silhouette can be seen from the other Harry's point-of-view from across the lake, but Hermione isn't next to the same tree, even though the spot she was standing in is visible. (01:44:20 - 02:01:05)
Continuity mistake: When the stone hits Harry, the very first time, in the shot inside Hagrid's, he yells, "Ow!" and as he turns the blue cup touches the wood tray. In the next exterior shot, the blue cup is closer to the birdcage. (01:24:55)
Continuity mistake: The Monster Book of Monsters' torn papers change amount/position in subsequent side and top shots when there has been no movement on the floor by the book or Harry nor any floor shaking by the train either. (00:15:20)
Continuity mistake: When Harry says, "I said we'll take you to the castle," to Pettigrew, you see Sirius pointing his wand at Pettigrew. When it cuts Sirius is standing next to Harry, but he is no longer pointing his wand. (01:32:45)
Chosen answer: It's not known what it is. It is left to the audience's imagination of what exactly is in the room or what some witch or wizard was doing in there. This is only meant to be a humorous bit and is unrelated to the plot. It didn't happen in the book.
raywest ★