Continuity mistake: When Marge floats out the patio door in the exterior shot her jacket lies flat over her skirt. In the next shot Vernon shouts, "I've got you Marge," as he grabs hold of her hands, and the bottom of her jacket is way up by her arms - note the blazer lining and her blouse. However, in the next shot the jacket lies straight and flat once again. (00:05:25)
Continuity mistake: When Hermione removes the blanket that makes Potter invisible you can see some snowflakes on his shoulder. It cuts and she says "Harry, what happened?", then it cut again and the snowflakes are gone. They could not have melted that fast. (01:04:55)
Continuity mistake: The chain on the Time-Turner changes length from when they go back in time, and to when Hermione explains the Time-Turner to Harry, one minute later. (01:43:15 - 01:44:35)
Continuity mistake: At the hospital, after Potter fell off his broom as Hermione says "No one blames you, Harry", you can see Ron standing behind her. At this time we can see the letter "H" on the cloth that is wrapped around the broom. Later, the letter "E" is visible instead. (00:54:45)
Revealing mistake: As Harry and Buckbeak fly over the loch, Buckbeak's foot trailing in the water leaves a wake, as it should. This wake should also disturb the ripples and waves that are already present on the surface of the water, but they do not. It is obvious that the wake effect was added in, but the foundation shot of the loch was not edited to help it make sense. (00:35:20)
Continuity mistake: On the Hogwarts Express, Lupin pulls out his wand to repel the Dementor attacking Harry. In the shot facing Lupin his shirt sleeve is mostly covered by his suit sleeve and he holds the wand a particular way. In the next close-up facing the Dementor, Lupin's arm is visible and a much greater area of his shirt sleeve is now seen and he holds the wand completely differently. (00:22:15)
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)
Audio problem: When Aunt Marge says, "Vernon, Vernon do something." and the dog charges at Vernon and bites him in his leg, you can hear Vernon scream in pain. At the same time you can see his lips move as he says something, but all we hear is screaming. (00:04:35)
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)
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 ★