Continuity mistake: When Senator Kelly is giving a press conference to declare his candidacy for President, at the start there is a flag immediately to his right. When the shot changes, after a few seconds the camera pans out and the flag has now moved several more feet to his right. (00:14:05)
Continuity mistake: When Sabretooth is watching Senator Kelly's press conference, his chair is directly facing the TV. After Jubilee turns off the TV and walks towards Sabretooth, his chair has now rotated roughly 90° clockwise. (00:14:47)
Continuity mistake: When Jubilee raises Sabretooth's arm restraint, the interior side of it is shown to extend all the way down to the arm rest. When the shot changes, it now has an opening for a person to move their arm through. (00:15:31)
Continuity mistake: When Sabretooth tells Jubilee that her powers are useless if she can't use her hands, the glove on her left hand turns from yellow to brown multiple times. (00:15:50)
Continuity mistake: Numerous episodes depict the War Room as being a circular room completely enclosed from the rest of the underground facilities. However, when Wolverine is confronting Sabretooth in the War Room, it is a wide open area with numerous corridors. (00:16:23 - 00:17:05)
Continuity mistake: When Wolverine says to Sabretooth "Be careful what you ask for," his arms are yellow. (00:17:05)
Continuity mistake: When Sabretooth is trying to force Wolverine's claws into his own face, the black part of Wolverine's mask on either cheek is incorrectly colored yellow. (00:18:13)
Continuity mistake: When Sabretooth is trying to force Wolverine's claws into his own face, they are next to a set of steps. When the shot changes, there are no steps anywhere near them. (00:18:46)
Audio problem: When Professor X says "I was wrong Wolverine. I should have listened to you," his mouth is completely closed. (00:19:50)
Continuity mistake: When Storm is saying "We failed, Professor, together," her lips are red. When the shot changes, her lips are brown. (00:20:00)
Continuity mistake: When Xavier is saying "We cannot afford to lose again," his fist is raised, and Storm is leaning over him. When the shot changes, his hand is resting on his hoverchair, and she is standing upright and further away from him. (00:20:05)
Continuity mistake: When Magneto is saying "Mutants will come to me by the thousands," he raises his right fist up near his face. He then begins lowering his hand, and when the shot changes, it is instantly down at his side. (00:20:29)
Continuity mistake: When Jubilee blasts Sabretooth through walls of the War Room and outside, it is shown to be on the mansion's ground level. Many other episodes however depict the War Room to be in the underground levels of the mansion, specifically in the episode "The Unstoppable Juggernaut" where the War Room is still intact after the mansion is destroyed from the ground up.
Continuity mistake: When Gambit is avoiding the electrified coils in the Danger Room, his normally black and red eyes are colored like a normal person and his gloves are entirely fingerless whereas they are usually only fingerless for the thumb, index and pinkie fingers. (00:02:15)
Character mistake: When Rogue asks Storm what her plan is for dealing with the closing walls, Storm says "You three stop the walls, I shall slow the ceiling." Besides Storm and Rogue, Jubilee, Jean Grey, and Gambit are also there, so Storm should have said "You four stop the walls." (00:03:12)
Continuity mistake: When the walls begin closing in on the X-Men in the Danger Room, the blue center of Jean Grey's outfit is incorrectly colored the same light-orange color as most of her outfit. (00:03:12)
Continuity mistake: When Storm is having a flashback to her childhood in a fit of claustrophobia, she is depicted as a Caucasian girl with red hair. (00:03:35)
Continuity mistake: When Rogue is thrown into the wall by Storm's wind, the green side of her uniform is incorrectly colored yellow. (00:03:52)
Continuity mistake: When Jean is first shown in her dress, it is a solid pink color. When she is walking down the sidewalk on her date with Cyclops, the midsection of her dress is now a lighter shade of pink than the rest. (00:04:34 - 00:05:18)
Continuity mistake: When Jean Grey is first shown standing in Wolverine's doorway, her arm is resting on the door with her elbow level with her shoulder. When the shot changes, her elbow is now level with her breasts. (00:04:34)
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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