Continuity mistake: When the people begin throwing tomatoes at Beast, the judge in the background is sitting down. When the shot changes, he is standing. (00:10:04)
Continuity mistake: The stains from the tomatoes that are thrown at Beast disappear from his jumpsuit. (00:10:05 - 00:10:55)
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 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: 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)
Other mistake: When Cyclops is turning on his communication device to talk to Storm, his fingernails have been drawn on his gloved hands. (00:18:50)
Continuity mistake: When Storm shoots lightning at the missiles, it is yellow. When the shot changes, it is blue. (00:19:40)
Continuity mistake: When Storm is free-falling after stopping the missiles, the communication device on her left side is flashing as Cyclops is speaking to her, and as her body rotates, it becomes the right side device that flashes. (00:19:53)
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: 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 Sabretooth is sitting in the hover chair in the War Room, the chair is shown to be hovering up and down in the wide shot, but when a closeup of Sabretooth is shown, the background behind him remains stationary, indicating the chair is also stationary. (00:04:35)
Revealing mistake: When the lab workers are running out of the plant as Magneto is wondering what Xavier looks like after so long, you can see the man in the lab coat and hard hat jerks backwards as he is near the flames. (00:07:53)
Other mistake: Whenever Rogue touches someone's bare skin with her own, it is accompanied by an energy surge to indicate she has drained them of their powers. However, when she is performing mouth-to-mouth resuscitation on Cyclops, the energy surge doesn't occur. (00:10:26)
Continuity mistake: When Rogue is blindly searching for Cyclops, the black circle with the red X on her chest is now a red circle with a yellow X. (00:11:14)
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)
Factual error: When Xavier is getting ready to get back into his hoverchair, you can see him raise himself to his knees, even though he is a paraplegic. (00:13:43)
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)
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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