Continuity mistake: In the first exterior shot looking through the Dursley's patio doors, as they have dinner, and later when Vernon runs after Marge, the threshold is wide, flat and all white. Below the glass on the doors the trim is narrow and at the very bottom it is wide. There is a keyhole opening (on the left door) under a particular style door handle and there is a wide double lip going round the entire edge of the left door. When Petunia runs out, the threshold is higher up and mostly brick, with a thin strip of white in the middle. The style of the patio doors under the glass is completely different, there is no keyhole, the handle style differs and there is no double lip on the door. Additionally, the large clay pots with plants, beside the doors, change from being glazed and shiney to being unglazed, its plants differ and things change position. (00:02:00 - 00:05:00)
Revealing mistake: When Ron and Hermione are arguing with Malfoy near the Shrieking Shack, Malfoy visibly flinches before he is hit by the first snowball. He's not looking in the right direction to see it coming. (01:02:15)
Continuity mistake: After leaving the Dursleys, Harry sits down on the pavement beside his trunk, with no room between the two. When he turns to look at the squeaking swings, in the shot from behind him, there is at least a foot of space between Harry and the trunk. Yet in the next shot that faces him, the trunk is beside him once again. (00:07:20)
Continuity mistake: After bowing to Buckbeak, Harry removes the chain from the ring on the wood post, with the crow sitting on it. In the close-up, the wood post with its metal hardware, and the actual black crow, all noticeably differ from the previous and following shots.
Continuity mistake: During the class with Hagrid, sometimes Ron has his Monster Book of Monsters under his arm and sometimes he doesn't have it. (00:33:35 - 00:34:55)
Visible crew/equipment: When Dumbledore, Fudge, and the executioner show up at Hagrid's hut (the first time), Harry, Hermione, and Ron sneak out the back then hide behind the pumpkins, and the mic pack bulge can be seen under Hermione's hoodie, at her side. (01:26:10)
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: 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: In the first Divination scene, Prof. Trewlaney reads Neville's cup then puts it down onto a saucer. However, in the next shot, Neville picks it up from the tabletop. (00:30:00)
Revealing mistake: In the scene in which Harry, under the guise of the Invisibility Cloak, is dragged by the Weasley twins into the castle by his arms, it's obvious that the twins are miming a person in between them. There is one point when they round the corner right before throwing him onto the stairs, the twins are pretty much side by side, there is absolutely no room between them for a person at that point. They then widen the space again right after they round the corner. (00:56:55)
Continuity mistake: When Potter comes down the stairs with his trunk, the strap on the trunk is bent backwards. When it cuts it lies normally on the trunk. (00:06:25)
Revealing mistake: When Hermione fakes reading the crystal ball, Trelawney insults her and Hermione knocks the crystal ball off the table. As the crystal ball leaves its stand it turns over and the tube used to create the smoke effect inside the ball is visible. Then as the ball rolls toward the stairs, there are no tubes visible. (01:19:55)
Continuity mistake: During CoMC class, after Hagrid coughs, says, "Ta da!" and gestures toward Buckbeak, there is a shot of the students and Hermione's Monster Book of Monsters lies open on the huge rock. In the next close-up of Hermione, her book is closed and partially buckled. When Ron asks, "Hagrid...what is that?" her book lies open again. Books lying near Hermione's change in consecutive shots as well, including the one held by the girl beside Neville. (00:33:20)
Continuity mistake: When Harry first meets the Minister of Magic in the Leaky Cauldron, and he is being reprimanded for running away "considering the state of things," the Minister places his hands on the back of a chair. His hands change position from shot to shot. (00:13:30)
Continuity mistake: When Stan Shunpike begins, "Welcome to the Knight Bus emergency transport for the stranded witch or wizard...," in Harry's close-up the lamppost is directly behind Harry. However, in the shot from behind Stan when Harry says, "I fell over," the post is about 6 ft away, to Harry's left. (00:08:25)
Continuity mistake: In the Leaky Cauldron, the Minister takes the lid off of a pot of pea soup. Yet after reprimanding Harry, he shakes Harry's hand and walks past the table, and you can see the lid is on the pot of pea soup. It isn't in any other shots. (00:13:05 - 00:13:55)
Continuity mistake: When Hagrid is telling Harry, Ron and Hermione that Buckbeak must be executed, you see Harry in the background sitting on a rock, then stand up when he hears the news and walk away from the rock behind him. In the very next shot from behind, Harry is sitting down again (the water ripple from the small stone is visible at Hagrid's left). (01:10:00)
Continuity mistake: When in the Leaky Cauldron, there is a man offering Harry food. He holds a bowl of nuts towards Harry, and in one shot he holds the bowl with two hands, yet in the following shot he is holding it with one hand. (00:12:50)
Continuity mistake: When Harry climbs out of tunnel into Honeydukes, the boxes on the stairs are straight up against the wall, including the box with the lollypops on the fifth stair. However, in the next shot from above, the box is farther from the wall for the effect. (01:01:00)
Continuity mistake: When Malfoy and his friends take off, after Harry has beaten them, you can see Hermione and Ron standing in the background with their backs to a fence. When it cuts to a closeup of them they are suddenly standing behind a tree. (01:00:30)
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 ★