Other mistake: When the tank falls through the hole in the bridge, the tank's occupants are impossibly shown to be clinging to the edge of the hole at the same time the tank is going over the edge, as if the tank and the occupants were occupying the same space. (00:09:40)
Continuity mistake: When the cameraman drops his camera, it lands on the ground and rests on a rock so that the lens is at a slanted angle. When the shot changes to the camera's point of view, it shows Apocalypse right side up, when he should be slanted to correspond with the camera. (00:10:14)
Continuity mistake: When Xavier is briefing the X-Men about Apocalypse, Storm is on Xavier's left, and as the camera pans up and to the left, you can see no-one is around her. When the shot changes, Cyclops and Rogue are suddenly next to Storm. (00:10:21)
Continuity mistake: When Xavier is saying "They can be appealed to, reasoned with," Jean Grey's back is entirely peach-colored, when there should be a blue stripe going down the middle of it. (00:10:36)
Continuity mistake: When Xavier, Jubilee, and Rogue are walking towards the end of the Blackbird's runway, their shadows on the wall show Rogue in front of Jubilee, but Jubilee is actually in front of Rogue. (00:10:51)
Continuity mistake: When Rogue is flying toward Adler's lab, you can see the building is several stories off the ground. When she flies in through the hole in the roof, the interior of the lab is on the top-level, whereas the previous episode showed that the lab was on the ground level. (00:12:55)
Continuity mistake: When Rogue is shackling Dr. Adler to the platform, she only applies the restraints to his arms and left foot, leaving the right foot unshackled. Moments after Adler reveals himself to Rogue to being Mystique, the right foot is now shackled as well. (00:13:31 - 00:14:08)
Continuity mistake: When Rogue is interrogating Mystique, she is standing in various places next to the platform depending on the shot. (00:13:45 - 00:14:08)
Continuity mistake: When Rogue positions the platform that Mystique is shackled to upright, Mystique's feet are close to touching the floor. A couple of shots later, her feet are suddenly several inches higher. (00:14:08)
Continuity mistake: When the statue is about to fall on Wolverine, his arms are colored yellow. (00:16:25)
Other mistake: After Gambit explodes the statue that was about to fall on Wolverine, there is no debris shown to be flying around them even though the statue was collapsing towards them. (00:16:30)
Audio problem: When Cyclops shoots an optic blast at War's feet during the battle at Stone Henge, the groan that War lets out is the same sound used whenever Wolverine's groans. (00:18:24)
Continuity mistake: The trap door that Apocalypse uses to escape suddenly disappears once Wolverine tries to claw his way through it. (00:19:35)
Continuity mistake: When Archangel is lamenting his actions, the communicator devices from Storm's uniform are missing. (00:20:15)
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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