Continuity mistake: After Wolverine carves "HERO" onto Cocteau's tombstone, he has to walk several feet away from the tombstone to get to Justine. When the shot changes, both of them are only a couple steps away from the tombstone. (00:19:15)
Continuity mistake: When Rogue and Gambit are playing pool, Rogue's arms are bare from the elbow down except a yellow wristband on each wrist. When Beast comes in with the mail, Rogue is wearing her usual green sleeves and yellow gloves. (00:04:00 - 00:05:10)
Continuity mistake: Kenny's hair goes from being light-brown to blonde. (00:05:50 - 00:11:00)
Continuity mistake: When Kirkland is going through photos of Rogue, he stops on a photo of the full X-Men team. When the shot changes, the photo he is stopped at is of Rogue and Cannonball. (00:08:25)
Continuity mistake: Gambit uses his staff to pole vault himself across the rooftops. When he lands, the staff has vanished. (00:09:30)
Continuity mistake: When Gambit jumps out of the ventilation shaft, there is no one around him. Then he is suddenly surrounded by guards who could not have converged on him so quickly unless they appeared out of thin air. (00:10:00)
Continuity mistake: When Gambit is restrained in the chair, his gloves alternate between being his usual gloves that are fingerless at the thumb, index and pinkie fingers, to not being fingerless, to him not wearing any gloves at all depending on the shot. (00:10:05)
Continuity mistake: The ice cream that Cannonball drops when Kenny confronts him disappears in subsequent shots. (00:10:50)
Continuity mistake: In one shot before the nurse shaves a patch out of Gambit's hair, the neck portion of his black headgear is flesh-colored. (00:12:40)
Continuity mistake: When Moira is asking the X-Men how they intend on contacting Lilandra, Jean Grey's face is colored yellow. (00:05:10)
Continuity mistake: When Trish Tilby is giving the news report, she is first shown to be in front of a gray news van. When the shot changes and for the rest of the report, she is standing in front of a blue screen. (00:05:30 - 00:06:45)
Continuity mistake: When Cyclops, Wolverine and Gambit are watching Morph giving a statement on the news while masquerading as Xavier, Cyclops' hair looks like a bowl-cut rather than the usual semi-shaggy look he sports. (00:06:20)
Continuity mistake: When Magneto is saying "You are the next step in man's evolution," the lower half of Sunfire's mask is flesh-colored. (00:11:55)
Continuity mistake: When Jean Grey is stating how Magneto's powers intensified her own, the left side of her costume around her abdomen is colored yellow whereas it is usually blue (the right side remains blue in this shot). (00:13:30)
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.
BaconIsMyBFF