Continuity mistake: When Harry is dragging Malfoy by his legs the snow on Malfoy's cloak change between the shots. (01:00:15)
Continuity mistake: When Harry attacks Malfoy, he pulls Crabbe's pants down. When Malfoy and Crabbe start to run up the hill, in one shot, Crabbe's pants are down by his ankles. In the very next shot, his pants are up near his waist and he wouldn't have had time to pull them up between shots. (01:00:30)
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)
Continuity mistake: When Harry lifts the lid in the Honeydukes cellar, in the first shot there are two gold pots, small and large, beside the table directly in front of him. Of course in the next shot, as the man climbs the stairs, only the short gold pot is beside that table. In the next shot, as Harry climbs out, the two pots' positions differ. (01:00:45)
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 Harry storms into the pub in Hogsmeade, the camera follows his footprints to the door, and at the door is a large clearing where there is no snow, because the ground is sheltered by the door's porch. Yet in the following shot the clearing has decreased greatly. (01:01:35)
Continuity mistake: When Malfoy and his friends bother Ron and Hermione, Harry shows up and messes with the three boys. He grabs hold of Malfoy's feet, lifts them in the air and pulls him across the snow. In the first close-up of the soles of Malfoy's boots, not a speck of snow is on them, though he was just walking in it. Then in the next close-up, his feet still in the air, the soles are now covered in snow. (01:02:45)
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: When Lupin is about to teach Potter the Patronus charm, you see Lupin walking with his hands in his pockets while saying "Do you have a memory? Allow it to fill you up. Lose yourself within it." When it cuts Lupin has his left hand up. (01:05:30)
Continuity mistake: When Potter is learning the Patronus charm, as he is facing the candle and is talking about his memory and saying "It's the happiest I've ever felt.". His hair has an extreme change in the next shot. (01:07:10)
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: 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: When Hagrid cries out, "Buckbeak's been sentenced to death!" in the close-up, Harry Ron and Hermione are visible at the shoreline behind him. However, in the next overhead shot Ron and Hermione are much closer to Harry along the shore. (01:12:50)
Continuity mistake: When Snape points his wand at the Marauder Map and says, "Reveal your secrets," you can see Potter has his right hand down. When the scene cuts, his right hand is holding the map. (01:13:00)
Continuity mistake: In the corridor when Harry shows the blank map to Snapes he is holding it only in his left hand. When the view switches he has both hands on it, and in the next shot is again holding it in one hand. (01:13:00)
Continuity mistake: During the scene where Snape confronts Harry roaming the hallways at night with the Marauder's Map, the position of the pull strings hanging down from Harry's sweatshirt hood changes several times between shots. At first the strings are tangled together, but during later shots the strings are hanging down apart, then back to being tangled, then apart again. This happens once more when Prof. Lupin and Harry are talking immediately afterwards in the Dark Arts classroom. (01:13:05)
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 is walking back to Trelawney with the ball, as he enters the room through the tight passage, you can see light is shining in. When it cuts to him entering the room the light is gone. (01:17:35)
Continuity mistake: In Divination, as Trelawney says, "The art of crystal gazing is in the clearing of the Inner Eye... Now what do we have here?" Ron sleeps with his elbow at the books in front of him and then wakes. In the next shot the books are between him and Hermione. (01:19:15)
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 ★