Continuity mistake: When the Weasleys give Harry the Marauders Map, Harry takes it from George with his left hand, yet in the next shot the map is in his right hand. (00:57:10)
Continuity mistake: After the Weasley's have handed over the Marauder's Map to Potter, George puts his wand on the Map while saying, "I solemnly swear that I'm up to no good." When it cuts to a closeup of the map, you can see the way Potter is holding it changes, and the way George's wand is on it changes. (00:57:25)
Continuity mistake: When the Weasley's have given Harry the Marauders Map, after one of them says "We owe it so much", Harry opens the map. When it cuts he opens it again. (00:57:35)
Other mistake: When Harry gets the map from Fred and George, he watches it and then one of the twins taps it and the contents fade away. But the text to the left, in shadow of the folded pages, doesn't fade. (00:58:15)
Continuity mistake: When Fred and George give Harry the Marauder's Map, Harry opens it up and on the right is Dumbledore's study. In the close-up shot of Dumbledore's study, the map is drawn with much more elaborate detail for fun and dramatic flair and the actual words of the interlocking circles are written on the map extremely differently than the previous shot. (01:00:00)
Continuity mistake: When Potter is messing with Malfoy and the other two kids outside the Shrieking Shack, as Potter drags down the cap on one of the kids, you can see the kid's scarf is suddenly tied. It wasn't tied in the earlier shot, and Potter could not have tied it that fast. (01:00:00)
Continuity mistake: After Fred and George hand over the Marauder's Map to Harry, he looks down and spots Dumbledore pacing in his study, though in this shot Harry does not actually look at the upper right corner of the map, where Dumbledore's study is located. (01:00:05)
Factual error: When Harry is beating up Malfoy and the two Slytherin boys in front of the Shrieking Shack, he grabs one of them by his scarf and rotates him around. The center of their revolutions should be at the end of the scarf (where Harry grabs it), but as there is no actual counterweight for the boy he has to balance only his own body, which moves the center of his revolution strongly towards him. (01:00:10)
Continuity mistake: When Harry is dragging Malfoy by his legs the snow on Malfoy's cloak change between the shots. (01:00:15)
Revealing mistake: When Malfoy and his friends are messed with by an invisible Harry, Malfoy is dragged along by Harry. In the SECOND shot, when Malfoy is dragged along (which is a closeup shot of Malfoy's legs up in the air) pay attention to the bottom right corner of the screen, and you can see a bare hand quickly move into view, quite close to the screen. This can't be Malfoy's hand because he has gloves on. Slo-mo is not necessary to see this. (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)
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)
Audio problem: Near the Shrieking Shack, when Malfoy says to Hermione, "How dare you talk to me! You filthy little mudblood!" cloaked Harry whomps him with a snowball. In the next wide shot, Crabbe visually asks, "Who is that?" though no sound is heard. (01:02:15)
Other mistake: While Hermione and Ron watch, cloaked Harry starts up with Malfoy and his two friends as they all stand in the snow. Most noticeable in the wide shot, when Harry spins the Slytherin boy, although the boy's feet visibly disturb the snow, Harry's feet do not make a mark - no footprints whatsoever. (01:02:30)
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)
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 ★