Continuity mistake: After the incident with the Whomping Willow, the dirt smudges all over Harry and Hermione's clothes change appearance and/or position in the following shots. (01:29:30)
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 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)
Continuity mistake: Harry moves closer to Snape at the Shrieking Shack, as he points his wand at the professor. In the first two shots Snape stands closer to the door, yet in the close-up as the spell hits he is farther from the doorway, so he can easily fly backwards for the stunt. (01:34:00)
Continuity mistake: At the Shrieking Shack, when Scabbers tries to run away, as he runs towards the small hole in the wall, the shape of the hole differs in the shot facing the rat's hind and the next shot facing Scabbers, just as he enters the hole. (Obviously before the hole enlarges to accommodate Peter.) (01:35:05)
Continuity mistake: In the scene where Sirius lies at the lake and Harry kneels next to him, Sirius seems unconscious, then opens his eyes in terror as he sees the Dementors. However, in the very next shot, which shows the two from above, his eyes are suddenly closed and there's no sign of movement in his face. Too big a change, too fast. (01:38:45 - 01:42:50)
Continuity mistake: When Harry and Hermione are back in time, Lupin's transformation happens a lot faster than the first time. Also, the first time, Hermione shouts "Harry!", then Sirius yells "Run! Run!", then Lupin howls. The second time it goes "Harry!", then howling, then "Run! Run!" (01:39:45 - 01:57:40)
Continuity mistake: When Harry first sees the Patronus with Sirius, from Harry's POV it is clear that the Patronus light contracts entirely into the wand, while the area around the wand is still visible, and then he collapses. However, when Harry casts the spell later into the movie, Harry collapses on the other side of the lake, while the light from the wand is still quite large. (01:41:00 - 01:57:00)
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: Immediately after Remus' and Sirius' fight (as werewolf and animagus dog), a wounded Sirius stumbles down a pathway towards the lake. Harry is only a few steps behind him. When the scene cuts to the next shot, Harry is now running down a wooded slope alone and spots Sirius lying next to the lake. Sirius, in his weakened and injured condition, could not have sprinted so far and so quickly ahead of Harry. The terrain isn't steep enough for Sirius to have rolled all the way to the edge, and he wouldn't have had time to get up and continue walking. (01:41:50)
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: In the first scene when Harry and Sirius are by the lake, Harry sees someone conjure a Patronus on the other side; initially the silvery form of a stag is seen for quite awhile, then the circular light that broadens. However, after Harry and Hermione go back in time, as the shot faces Harry, he yells, "Expecto Patronum!" and immediately the wand emits circular light that magnifies and repels the Dementors. (01:44:05 - 02:01:00)
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 Potter and Hermione is following back in time down to Hagrid's you see Hermione leaning against a column before putting her arm down. When it cuts back she is still leaning against the column. (01:45:25)
Continuity mistake: When Potter and Hermione watch Fudge, Dumbledore and the executioner heading down to Hagrid's, Hermione says "Fudge is coming." Potter then turns his head. When it cuts he turns it again. (01:46:40)
Continuity mistake: In the hospital wing, when Hermione says, "Sorry Ron, but seeing as you can't walk," the camera pans around her and Harry. Before she turns the timeturner, the bed that Harry was lying in is visible and the blankets which were folded neatly in the previous shots are now off and very messy, and the positions of the tall blue screen and chair near the bed are also completely different. Later, when they return, the bed is perfectly neat and the chair is pushed back again. (01:47:10)
Continuity mistake: When Harry and Hermione travel back in time, Harry walks towards Buckbeak, planning to save him. There are pumpkins around Buckbeak and there is also a black cauldron near him too. The pumpkins and the cauldron move between shots during the scene as do other items in the background, and nobody touches them. (01:48:25 - 01:49:25)
Continuity mistake: When Harry goes to unchain Buckbeak, in the closeup he is holding the metal ring with his left hand after getting nipped by the crow, yet in the following wideshot his hand is below the ring, and he is now holding the metal chain. (01:48:40)
Continuity mistake: When Harry and Hermione are back in time, Dumbledore, Fudge, the Executioner and Hagrid come out of Hagrids hut to execute Buckbeak and they find Buckbeak has gone. Then Dumbledore says "I don't think the minister's suggesting you had anything to do with this" and in the wideshot Dumbledore steps up onto the bottom step of the stairs leading to the hut, and stands right by Hagrid. Yet in the following closeup as Dumbledore says "How could you..." Dumbledore is now not on the bottom step, but standing on the path much further away from Hagrid. (01:50:10)
Continuity mistake: After Potter and Hermione have escaped with Buckbeak, Dumbledore says, "I don't think the Minister's suggesting you had anything to do with it." At that time you can see three crows on the roof above Hagrid, and one of the crows takes off. When the scene cuts back there are still three crows on the roof. (01:50:10)
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 ★