Continuity mistake: When Dudley is hit by the first button that flies off Aunt Marge, we can see a table beside him with a lamp and a picture on it. When it cuts to Dudley lying on the floor, we can see the lamp and the picture have changed position. (00:04:50)
Continuity mistake: When Aunt Marge's chair starts to float up, in the close-up of her legs, her feet are at least a foot off the ground and the chair even more. However, after her necklace pops, Vernon yells, "Down boy!" at Ripper, she lets go of the table and in the next wide shot, her feet are still well under the table and the chair is still touching the floor - this shot is spliced from the earlier shot, just after Ripper first bites Vernon's foot! (00:04:50)
Continuity mistake: When Aunt Marge flies off, she starts pulling the tablecloth and some food stays on the table but in each of the following shots where there's a view from the side, the table is clean. (00:04:55)
Continuity mistake: When Aunt Marge is inflating and floating to the ceiling, she grabs the table cloth and continues going up and take the cloth with her. Then when one of her shirt buttons pops and hits Dudley you can see that the cloth is not moving but has slid across the table a bit. It cuts to a close up of Marge and the cloth does not move, it then moves to the wide shot of the whole table and the cloth continues to move. The other button pops, hitting Dudley again, and the cloth stops moving again. (00:04:55)
Continuity mistake: When Aunt Marge is blowing up, one of her buttons pops off and hits Dudley in his forehead making him fall to the floor. We see him lying on the floor beside the table but when it cuts he is suddenly getting up right at the table. (00:04:55)
Continuity mistake: When Aunt Marge is about to fly out the door, we can see Uncle Vernon leaning on the table with his back against the door and the dog biting his left foot. When it cuts to Aunt Marge coming out the door, we see Uncle Vernon facing the door and the dog is biting his right foot. (00:05:10)
Continuity mistake: When Marge turns upside-down, just before floating out the dining room door, the bottom of her jacket falls towards her arms and the back of her jacket is deliberately pinned to her blouse and skirt, so as not to fall entirely down. (00:05:15)
Continuity mistake: When Marge flies away, she is pulling the tablecloth off. At the bottom of the frame are candles and a green bottle. In the very next shot both of these are gone. (00:05:20)
Continuity mistake: When Marge floats out the patio doors after Vernon yells, "Stop!" there is a horizontal tear along the vertical one at the back of her jacket, that is gone in the last shot of her after Vernon lets go. (00:05:25)
Continuity mistake: When Marge floats off, Vernon is holding onto her, and Marge's dog is biting Vernon's trouser leg. In a closeup the dog is pulled well onto the Dursely's back lawn, as he bites Vernon's trouser leg, yet in a following wideshot the dog is dragged from the patio and onto the lawn once again, whilst biting the trouser leg. (00:05:25)
Continuity mistake: When Marge floats out the patio door in the exterior shot her jacket lies flat over her skirt. In the next shot Vernon shouts, "I've got you Marge," as he grabs hold of her hands, and the bottom of her jacket is way up by her arms - note the blazer lining and her blouse. However, in the next shot the jacket lies straight and flat once again. (00:05:25)
Continuity mistake: Between the shots of Marge floating out of the house and later when Petunia runs to Vernon on the grass, there are many significant changes. The short brick walls that edge the Dursley garden are actually different bricks, different grout and are even aligned differently between these shots. The bushes along the wood fence are at least 2-3 ft away from the corner bricks in the first shots, but in the last shot are aligned with the corner. The height of those bushes go from being way above the top of the wood fence to being at least a foot below. In the first shots there are small metal plaques that are attached along the top of the wood fence, but in the last shot they are gone. (00:05:30)
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: When Vernon holds Marge's hands as she floats up, in the shot just before she yells, "Don't you dare!" Dudley stands behind Petunia with the napkin hanging from his collar. After she floats away screaming, in the close-up of Dudley the napkin stains differ and it now has a glob of white cream which he promptly wipes off and eats. (00:05:40)
Continuity mistake: As Vernon watches Marge float away, he is on his knees on the grass in the backyard, with Petunia beside him. Still on his knees as Vernon shouts, "Please!" in the shot from inside, his position on the grass is now centered with the door, so as to be visible for this shot. (00:05:50)
Continuity mistake: As everyone watches Aunt Marge start to soar up into the air while in the yard, the position of the white lace tablecloth, which hangs off the table at this point and the things upon it, differ in the exterior shot looking in towards the dining room and the following interior shot of the table. (00:05:55)
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)
Continuity mistake: When Potter points his wand at Vernon and Vernon says, "You're not allowed to use magic outside school," you see Vernon holding his hands down. When the scene cuts back to Vernon, he has his hand by the banister. (00:06:25)
Continuity mistake: When Potter points his wand at Uncle Vernon you can see his index finger on the wand. When it cuts his index finger is pulled back. [Harry has obviously jerked backward when Uncle Vernon approaches him -- Vernon is obviously closer in the second shot -- and it would be a natural reflex to withdraw his finger as well.] (00:06:25)
Continuity mistake: When Vernon says, "You've nowhere to go," to Potter, you see Vernon grab the banister. When it cuts, the way he holds the banister changes. (00:06:30)
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 ★