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: When Aunt Marge is round and everybody is eating, in one shot Dudley is spooning something off of his plate, yet in the following shot his spoon is up in his mouth. (00:02:25)
Continuity mistake: As Harry is about to drop his shoe on the floor in front of the Monster Book of Monsters, there is a closeup of Hedwig sitting on the chair. When it cuts to a wide shot, you can see that Hedwig has moved to farther to the left on the chair. (00:15:15)
Continuity mistake: As the Monster Book of Monsters falls to the floor and chases Harry's feet, the ripped seat cloth of the chair Hedwig sits on is visible. This ripped seat cloth changes significantly a total of four times in the following shots. (00:15:15)
Continuity mistake: When Trelawney asks Ron to look in Harry's cup and read the tea leaves, the Grim within the cup is visible. When Harry looks in the cup the Grim is different, for example, it has an open mouth in this shot. (00:30:20)
Continuity mistake: After Harry leaves the Dursleys, Sirius the dog shows up behind a park bench surrounded by dimly lit thick bushes. When the Knight Bus arrives, the bench is visible across the street and now it's brightly lit and the trash container beside the bench is clearly visible. Then, before Harry boards he has one more look at the bench and it is just as dark as the first shot. (00:08:00)
Continuity mistake: When Trelawney is looking in Neville's cup, a white cup is in front of a saucer on the table. When it cuts the cup has moved to the other side of the saucer. (00:28:55)
Continuity mistake: When Harry and Hermione travel back in time, Harry walks towards Buckbeak, planning to save him. There are pumpkins around Buckbeak and there is also a black cauldron near him too. The pumpkins and the cauldron move between shots during the scene as do other items in the background, and nobody touches them. (01:48:25 - 01:49:25)
Continuity mistake: When Dumbledore first introduces Lupin as the new Defence Against the Dark Arts teacher, the camera pans to the Gryffindor table. You can see that Ron and Hermione are sitting opposite each other with their dinner sets in front of them. Then Malfoy insults Harry, then when it cuts to Ron saying "Shove off Malfoy" Ron is now sitting opposite the girl who was beside Hermione and not Hermione herself, and the girl couldn't have just moved across because all of her dinner set is in front of her too, perfectly set out. (00:24:05)
Continuity mistake: On the Hogwarts Express, Lupin pulls out his wand to repel the Dementor attacking Harry. In the shot facing Lupin his shirt sleeve is mostly covered by his suit sleeve and he holds the wand a particular way. In the next close-up facing the Dementor, Lupin's arm is visible and a much greater area of his shirt sleeve is now seen and he holds the wand completely differently. (00:22:15)
Continuity mistake: The second time Harry conjures the patronus charm to save Sirius and the other Harry from the dementors, Hermione is standing next to the tree behind him. The first time he uses it, his silhouette can be seen from the other Harry's point-of-view from across the lake, but Hermione isn't next to the same tree, even though the spot she was standing in is visible. (01:44:20 - 02:01:05)
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 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: When entering the Hippogriff paddock, there is a shot of Hagrid stepping over the wall with the children behind and the ground is sunlit. Then it cuts to a wider shot and the ground isn't sunlit. (00:30:45)
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.
Continuity mistake: When Harry stands in front of the Gryffindor dorm and says the password, the door opens inwards. But when the shot changes to inside the dorm, there is no open door visible. (00:27:40)
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 ★