Other mistake: When Rogue is hovering above Muir Island, she pulls out a book to confirm she's in the right place, and the picture of Muir Island in her book shows it to have three smaller islands on its south side. When she lowers the book to look at the actual island, only the large island shown on the southwest side in the book is there. She's only hovering a few hundred feet above the island, so even though the other two islands were small, they should still be visible. (00:09:48)
Other mistake: When Rogue begins flying towards Cable after disarming him, she is only about 30 feet away from him. As she is flying towards him, he takes the time to pull a plasma grenade from his belt, pull out the pin with his mouth, and then throw it at her. In the time it took him to do all of that and given the speed at which Rogue was flying towards him, she should reach him well before he could throw the grenade at her. (00:18:05)
Other mistake: When Gambit, Storm, and Jubilee get into the back of the taxi, you can see the window seat behind the driver is unoccupied, which would suggest the three of them are occupying only two of the backseats. (00:12:51)
Other mistake: When Wolverine is walking around the camp after Sabretooth attacked it, he doesn't leave any footprints in the snow, even though Sabretooth's footprints are there. (00:14:52 - 00:15:36)
Other mistake: When the helicopters are attacking Magneto, they are firing their guns at him, and then he destroys them, at which point you can see the occupants parachuting away at the same time the helicopters explode. There's no way they could have been operating the guns and then jumping out of the helicopter to safety in one second. (00:06:01)
Night of the Sentinels: Part 1 - S1-E1
Other mistake: In the scene where Professor X uses his psychic powers to deduce that Jubilee is trying to escape the mansion, there is a semi-dissolve edit that simultaneously shows a close-up of Professor X with his left hand on his forehead and a counterpart image of Jubilee hiding around the corner. If you look closely at Professor X in the counterpart image of Jubilee, his left arm and hand are shown to be on his hover-chair's armrest and not his forehead.
