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: In the first exterior shot through the back patio door, as the Dursleys eat, the kitchen window and patio set below are visibly quite far from the white patio enclosure. Later, when Vernon falls to the ground as Marge floats away, Petunia runs to him and now the kitchen window, on a supposed brick wall, is actually right beside the white patio enclosure. Adding to the absurdity, the entire house is in the opening shot of the film and that middle part of the wall is conspicuously missing. Additionally, even the bricks and stone top of the seat wall between the tiled patio and grass have changed. (00:05:35)
Continuity mistake: At Hagrid's, when Harry, Ron and Hermione are there the first time in the film, there is a large birdcage, blue cup and saucer, watering can and small wood planter (with seedlings) on the windowsill. Later, when Hermione throws the first stone, as the stone flies through the window the watering can and blue cup's positions differ and the wood planter and large birdcage are gone. When she throws the second stone they are back on the windowsill. (01:24:05 - 01:52:20)
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, Ron, and Hermione are in Hagrid's hut prior to Buckbeak's execution, a stone flies in the window and strikes a pot, splitting it pretty much down the middle. There are two major shards. However, when Harry and Hermione 'relive' this moment from their position among the pumpkins, the stone (thrown by Hermione) breaks the pot in a very different pattern, with smaller pieces (and more of them). Since the same event is just being played through in time again, the pot should have broken exactly the same way both times. (01:24:45 - 01:51:15)
Continuity mistake: As the Knight Bus begins to appear, Harry falls back onto the ground, leans on his arms and in the front shot his sweatshirt is off his right shoulder, but in the next side shot, as he still leans on his arms, both sides of his jacket are properly on. (00:07:55)
Continuity mistake: When Hermione and Harry hide behind the pumpkins, Hermione says, "Come on! We're coming out the back door. Go!" As HRH run out of Hagrid's, Hermione and Harry run to hide behind the trees. In the shot facing the two, with the pumpkins and Hagrid's behind them, the blanket on the ground beside the pumpkins is visible, though it is gone thereafter. (01:52:00)
Continuity mistake: When Harry boards the Knight Bus in the exterior shot, the curtain in the small window at the stairs is pushed open towards the outside of the bus. However, in the next interior shot the curtain is pushed open towards the inside of the bus. (00:09:00)
Continuity mistake: When Sirius flies off on Buckbeak, the ground on which he takes off from is a perfectly clean stone ground with nothing on it. Yet after Sirius has flown off, Harry and Hermione run across the same ground, only now it is covered in dead leaves, grass and mud, etc. (01:59:40)
Continuity mistake: When the jar is smashed in Hagrid's hut, the lid stays on the smashed jar, yet when Hermione picks up the stone which smashed the jar, there is a closeup of her hand holding the stone and you can see the lid of the jar on the table. (01:21:30)
Trivia: In the end credits (approx 2:14:11), where the Motion Control Camera crew are listed, there are two pairs of shoe shapes showing in the lower left hand corner tower. Borrowing a quote from the film, "I swear [they] are up to no good.", because the shoes are positioned in such a way that it gives the appearance that they are engaged in a particularly adult diversion.
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.
Chosen answer: Fred and George used the map to aid them in their mischievous activities at Hogwarts, and probably had little interest in what their little brother was doing or who he might be with at any given time.
raywest ★