Continuity mistake: In the shot where Hagrid is telling Harry, Ron and Hermione that Buckbeak is going to be executed, you see Hermione (in the background) turn her head away and put her hand on her hip. In the next shot, which is a reverse shot and shows the actors' backs, she is still looking at Hagrid with her hands by her sides. (01:10:05)
Continuity mistake: Hagrid stands up and knocks over all of the glasses on his table at the beginning of the year. In the next shot, look to the left of Hagrid, between two candlesticks. A single glass is sitting upright on the table. In the next shot when Hagrid sits back down, none of the glasses are upright, but with the position the glass was in it should've been visible in this shot. (It's a bit hard to see, and it was spotted in widescreen.)
Continuity mistake: When Scabbers bites Ron and escapes, he and Hermione are standing very close together, but in the next shot they're further apart.
Continuity mistake: When Parvati is stepping up to the Boggart, Harry is standing behind her, but while it's Parvati's turn it is not Daniel Radcliffe, it's noticeably his stand-in instead. (00:43:30)
Continuity mistake: When entering the Hippogriff paddock, there is a shot of Hagrid stepping over the wall with the children behind and the ground is sunlit. Then it cuts to a wider shot and the ground isn't sunlit. (00:30:45)
Continuity mistake: When Harry and Hermione are running from the werewolf, they hide behind a tree and start edging around it to avoid the werewolf. When they are eventually seen by the werewolf, Harry is at least a foot behind Hermione but in the next shot he is beside her.
Continuity mistake: When Marge arrives, as she walks towards Petunia, there are two gold trim bars installed between the carpet edges and kitchen floor - one in the doorway and another between the kitchen counter and wall. Both disappear in the following shots. (00:02:00)
Continuity mistake: When Harry goes to the table to clean up Marge's broken glass and when he stands at the counter as Marge blows up, there is a large rug in the kitchen, under the center cart, whose edge reaches the counter stools. When Harry storms downstairs with his trunk, Petunia and Dudley stand at the kitchen doorway and the rug is gone - it would be visible if it was on floor. (Likewise, the rug was gone when Marge and Ripper arrived, but it could be presumed that the rug was laid out before their meal.) (00:03:50 - 00:06:40)
Continuity mistake: When Sirius and Lupin cast a spell to change Pettigrew from a rat and back into human form, he is fully clothed, as was Sirius when he changed from a dog. Later, when Pettigrew changes back into a rat to escape, his clothes remain behind as he shrinks.
Continuity mistake: Hermione's blue shoes look different in a couple of scenes, from when they were walking down to Hagrid's hut compared to right after Lupin attacked them.
Continuity mistake: Hermione and Ron's feet seem really close together after Buckbeak's "execution", but after Scabbers bites Ron their feet are suddenly much further apart.
Continuity mistake: When Harry, Ron and Hermione are in the shrieking shack Lupin comes in and says "Finally the flesh reflects the madness," look at the left side door behind him, it is facing outwards then it turns inwards in the next shot of him.
Continuity mistake: When Harry stands in front of the Gryffindor dorm and says the password, the door opens inwards. But when the shot changes to inside the dorm, there is no open door visible. (00:27:40)
Continuity mistake: When Harry drops the Monster Book of Monsters, the scraps of torn paper are already lying around Harry's feet before the book hits the floor.
Continuity mistake: When Harry is meeting the boggart it before it turns to a side view look at the girl to the left of Hermione, she is laughing, it changes to the side view and she is just standing there. It happens with Lupin too - in the side view he is playing with his wand then it switches to him and he isn't.
Answer: This didn't happen in the book. It appears to be done purely for comic effect in the movie, showing Dumbledore's eccentric and quirky nature. He's seemingly oblivious to what he's doing and how it affects Ron.
raywest ★