Continuity mistake: When Tom pushes Harry to the chair you see him pushing with one arm only. When it cuts you can see him pushing with both arms. (00:12:40)
Continuity mistake: When Harry unbuckles the belt around the Monster Book of Monsters, the belt lies open, across the bench. As the book chomps at Harry, in the shot behind Harry's feet the belt is curled up on the floor, to the side of the bench. (00:15:05)
Continuity mistake: When the executioner goes to chop the pumpkin (the second time), you see Fudge reaching for a crow on his hat. In the next shot, both his hands are at his side.
Continuity mistake: When Harry falls backwards onto the pavement, after seeing Sirius the dog, in the shot facing Harry the trunk lies halfway up on the pavement. However, in the next shot as the Knight Bus nears, only the very top edge of the trunk leans on the pavement. Yet in following shots it is halfway up the pavement again. (00:08:10)
Other mistake: When Harry is talking with Arthur Weasley at the Leaky Cauldron, the number '301' (colored in white) digitally pops up right underneath the wanted poster. The composite people neglected to remove it. This mistake occurs in a DVD widescreen version, and not visible in all versions. (This is not referring to Sirius Black's number '390' written on the paper that Sirius holds in the poster). (00:16:50)
Continuity mistake: During Hagrid's class, when Malfoy stands before Buckbeak as the Hippogriff rears up, in the wide shot facing Buckbeak, Malfoy lifts HIS left arm with his right arm still down at his side. However, in the next close-up facing Malfoy, HIS right arm is now lifted high up. (This has nothing to do with camera angles.) (00:37:55)
Continuity mistake: As the Knight Bus stops outside the Leaky Cauldron we see Stan Shunpike fold the newspaper as Harry flies forward. When it cuts we see Stan Shunpike fold the newspaper again right before Harry hits the window. (00:11:40)
Audio problem: When Aunt Marge asks Vernon for "a bit more" brandy the second time, her mouth doesn't move. (00:02:45)
Continuity mistake: When Harry falls back after being startled by Sirius the dog, the Knight Bus headlights shine glaringly bright light all over Harry and the trunk. Yet in the next shot facing the oncoming Knight Bus, Harry and the trunk are barely lit by the headlights, which are nowhere near as bright. In the previous shot the light is obviously provided by spots. (00:08:10)
Continuity mistake: The first time Dumbledore knocks on Hagrid's door, you hear him knocking three times. Later when Potter and Hermione have travelled back in time you hear Dumbledore knocking three times, rapidly followed by four more knocks. (01:21:55 - 01:47:15)
Audio problem: At Hagrid's, as we are hearing Fudge's voice saying, "The Hippogriff known as Buckbeak, hereinafter called the condemned, shall be executed..." it is actually Hagrid that we see talking, as we see them standing at the window. (01:26:00)
Other mistake: When Fred and George pass on the Marauder's Map to Harry, we see the map start to reveal itself. As it does Harry starts to read "Messrs Mooney, Wormtail, Padfoot and Prongs." Harry reads the word Messrs before it even appears on the page.
Continuity mistake: When Harry, Hermione, and Ron are hiding behind Hagrid's pumpkin patch in an attempt to hide themselves from Fudge and Dumbledore, Hermione turns around at the sound of a 'crack' in the forest, she then turns to her left and runs with the others. Later, when seen from Hermione's view reliving the past, Hermione at the pumpkins turns to her right before running with the others. (01:26:20 - 01:52:20)
Revealing mistake: When Harry first opens the Monster Book of Monsters, when looking closely, you can see the hollow part of the book that spits out the paper. Easiest to see when Harry is looking under the bed. (00:15:40)
Continuity mistake: When Trelawney is walking towards the table that Potter, Ron and Hermione are sitting at, you can see the book on the table is closed. When Trelawney gasps it cuts to Ron and you can see the book is actually open. (00:29:00)
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: When the Whomping Willow kills the blue bird flying towards Hagrid's home, the loose branches from one shot are not visible in the second shot. (00:29:05)
Continuity mistake: When Ron gets Scabbers back in Hagrid's hut, immediately afterwards Hermione says, "I think you owe someone an apology". Later, when future Harry and Hermione hide behind the pumpkins by Hagrid's hut, you can see Ron getting Scabbers back. So right after this Hermione should be saying, "I think you owe someone an apology." But future Harry and Hermione talk for a little bit, and when they're done, Hermione says the line. Shouldn't this line have already passed? (This can be easily checked on the closed captioning.) (01:21:25 - 01:47:00)
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)
Continuity mistake: When Harry first reaches Lupin's office, as Lupin is packing, the Marauder's Map lies open on the desk. The map folds change position when Lupin says, "I saw you coming." (02:06:10)
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 ★