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)
Continuity mistake: When Sabertooth is attacking the courtroom, he knocks out three guards with a chair. A couple of shots later, only one guard is on the ground, and when the shot changes again, none of the guards are on the ground anymore. (00:11:15)
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 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 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 Magneto topples Xavier out of his hoverchair, there are two white rectangles on the hoverchair that briefly turn yellow. (00:12:11)
Continuity mistake: After Wolverine says "Let's go kick his butt," he turns his head and you can see his ear changes color from white to the same color as the rest of his flesh. (00:04:15)
Continuity mistake: When Xavier says "Homo superior," his left hand is raised. When the shot changes, his hands are clasped together on the desk in front of him. When the shot changes again to over his shoulder, his hands are nowhere to be seen. (00:03:58)
Continuity mistake: When Xavier says Magneto believes mutants are the next stage in human evolution, the gray nameplate on his desk is centered. When the shot changes, it is now colored brown and has shifted to Xavier's right, near the computer monitor. Additionally, a folder appears on the desk between shots. (00:04:01)
Continuity mistake: When Magneto drops Wolverine, Storm and Cyclops onto the ground, Wolverine and Cyclops are lying mostly perpendicular to Storm. When it changes to a shot of them getting up, they are all parallel to each other. (00:17:18)
Continuity mistake: When Xavier is using Cerebro to look for Magneto, his blue and black tie turns yellow when Jubilee says "Professor?" When Storm says "Charles, are you all right?", it is back to being blue and black, and the blue stripes turn yellow before our eyes. (00:11:41)
Continuity mistake: During Beast's trial, Wolverine and Cyclops are shown in several wide shots to be sitting in the gallery on Beast's side of the courtroom. However, when Sabretooth enters the courtroom, Wolverine and Cyclops are suddenly on the prosecutor's side. (00:08:25 - 00:10:57)
Continuity mistake: When the bailiffs are escorting the unruly civilian out of the courtroom, the members of the gallery behind the prosecutor are different and fewer in numbers than they were earlier in the scene when the prosecutor was making her case against Beast. (00:08:29 - 00:10:22)
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 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 shoots lightning at the missiles, it is yellow. When the shot changes, it is blue. (00:19:40)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When Jubilee rings the doorbell at the end, it is black. When the shot changes, it is now gray. (00:20:36)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When Cyclops first blasts the Sentinels in the factory, the part of his bandolier around his communication device is incorrectly colored red. (00:18:15)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When Gyrich both enters and exits the White House exercise room, the file folder under his arm is the size of a briefcase. When he angrily throws the folder, it is now the standard file folder size. (00:14:45 - 00:15:17)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When the pool hall patron is pleading Cyclops to put his glasses back on, the yellow patch on his vest turns red. (00:14:20)
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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