Factual error: When Rogue is flying the dome up to the top of the mansion, she is flying at a diagonal angle and using a rope to tow the dome behind her. On its way up from the ground, the dome is also at a diagonal angle, when its mass along with the force of gravity and the slow speed at which Rogue is moving dictate that the dome should swing like a pendulum. (00:06:10)
Continuity mistake: When Cable has broken into Warren's lab from the balcony, the doorknobs on the double-door are intact. As the scene progresses, one or both doorknobs will disappear and reappear, and the broken glass on the one door will be intact. Additionally, when the opened door is first shown, there are a couple of broken pieces of glass on the floor next to it. When the shot changes, the pieces of glass are gone. (00:02:35 - 00:04:30)
Revealing mistake: When Warren's girlfriend is looking for him in his lab, she is startled by Cable who is hiding behind the door and slams it shut once she enters the room. When she is startled and looks back at Cable, the animation is not very fluid. As she is turning around to look at Cable, her "onion skin" form remains, making it look like there are two of her. (00:03:35)
Continuity mistake: When Cable blasts Warren off the balcony, Warren falls and drifts into the snow a couple feet, leaving an impression of his shape in the process. When he recovers, he emerges from completely under the snow as if he were buried, but the impression is still there in the snow moments later when he retreats, so it could not have refilled itself with fresh powder and buried him. (00:03:10 - 00:04:30)
Continuity mistake: When Cable grabs Warren through a shelf on his bookcase, he knocks several books onto the floor. When Warren pushes the bookcase over, there is an overhead shot of the floor surrounding the bookcase for several feet in each direction and there are no books visible on the floor. (00:02:50)
Continuity mistake: When Warren shoots his blaster through the bookcase, the blast goes through some books/file folders that say "DNA Test 6" and "DNA Test 7" while "DNA Test 4" and "DNA Test 5" are warped out of shape. When he pushes the bookcase over, the two warped books/file folders are back to normal. (00:02:50)
Continuity mistake: When Warren's girlfriend is saying "They say you keep a mad scientist up here," the earring on her left ear goes from being comprised of five gray circles, to four, and then back to five in the same shot. Both of her earrings are then comprised of four circles for the remainder of the scene. (00:02:10)
Continuity mistake: When Gambit and Wolverine are about to fight each other, Wolverine's claws are extended, and Gambit has a kinetically charged playing card raised in his right hand. When Rogue intervenes, Wolverine's claws are suddenly retracted, his hands are incorrectly colored white, and Gambit's right arm is down at his side, not holding any card. A couple of shots later, Wolverine's claws are once again extended. (00:07:15)
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)
Answer: Chris Potter, the original Gambit voice actor, did indeed quit the role in the 4th season. His last episode was The Phalanx Covenant Part 1 so it seems reasonable that Fox would limit the use of the character even though it was recast. It doesn't appear that Potter left the role due to animosity, he stated in an interview that he wished to play Gambit in the first live action X-Men film.
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