Continuity mistake: When Beast is theorizing that Xavier was coerced into contacting them, Gambit is sitting upright. When the shot changes, Gambit is now slouched in his chair (note his head is higher than the headrest in the first shot). (00:20:05)
Continuity mistake: When flashes of the different X-Men's faces are being shown while Xavier is being hypnotized by Sauron, Gambit's eyes are brown with white sclera, when they should be red with black sclera. (00:18:46)
Continuity mistake: When Sauron is hypnotizing Xavier, the space between Xavier and Magneto is greater than previously shown. (00:16:11 - 00:18:29)
Continuity mistake: When Magneto, Kazar, and Xavier are ambushed in the citadel, they are standing near the doorway leading to the stairs. When the shot changes, they are suddenly several yards into the room. (00:14:55)
Continuity mistake: When Kazar is taming the plesiosaur, its color changes from gray, to brown, and back to gray. (00:14:00)
Revealing mistake: When Wolverine notices Slab running off with Jean Grey, you can see the edge the animation cel moving across the screen from left to right. (00:12:34)
Continuity mistake: When Morph is performing his one man show, he is standing in front of a red and yellow stained-glass window. After he drinks the potion, the background behind him is now dark blue draping. It then becomes the stained-glass window again after he transforms into Mr. Hyde. (00:05:35 - 00:06:00)
Continuity mistake: When Amphibious is saying "Now we take them to the master," he is standing behind Lupo and Xavier. A couple of shots later, he is standing several feet away from them, next to a cliff wall. (00:04:45)
Continuity mistake: When Magneto is saying "Nicely played, Charles," the X emblem on Xavier's left shoulder is missing. (00:03:17)
Continuity mistake: In the wideshot of Magneto and Xavier scaling the cliff, Xavier is shown below and to the left of Magneto. When the shot changes, Xavier is now directly beneath Magneto. (00:02:25)
Continuity mistake: When Xavier is telling Kazar that Amphibious told him the Savage Land mutates were following a new master, his black shirt is suddenly the same color as his flesh. (00:09:47)
Mojovision - S2-E11
Audio problem: When Magneto is saying "the creature attacking the woman," his mouth only moves for the first two words. (00:20:23)
Mojovision - S2-E11
Continuity mistake: When Spiral is teleporting the X-Men back to Earth, the right side of Jean's outfit is blue, when it should be peach-colored, like the left side is correctly shown to be. (00:18:33)
Mojovision - S2-E11
Continuity mistake: When Mojo is saying "Go to something," the white sclera of his eyes is incorrectly colored the same green color as his skin. (00:17:30)
Mojovision - S2-E11
Audio problem: When Mojo is saying "Control room, what are you doing up there?", he doesn't press his lips together at the end of the word "room" in order to pronounce the M sound. Instead, he is shown clenching his teeth together. (00:17:19)
Mojovision - S2-E11
Revealing mistake: When Jean is dodging the Punisher robot's gunfire, the edge of an animation cel is visible, most noticeable when she is starting to form a telekinetic bubble around herself. (00:16:38)
Mojovision - S2-E11
Continuity mistake: When Mojo is saying "Control room," Rogue is suddenly missing from the cube that the X-Men are trapped in. She reappears in the next shot. (00:09:58)
Mojovision - S2-E11
Continuity mistake: When Mojo is telling Cyclops that he can write him out of the first act, the middle of Jean Grey's outfit is peach-colored, when it should be blue. (00:08:51)
Continuity mistake: When Morph collapses to his knees in his dressing room, his yellow waistband is now white. (00:07:00)
Continuity mistake: When Beast is noting how odd Xavier's message was, the sclera of Gambit's eyes are white, when they should be black. (00:19:34)
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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