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)
Other mistake: When the helicopters are attacking Magneto, they are firing their guns at him, and then he destroys them, at which point you can see the occupants parachuting away at the same time the helicopters explode. There's no way they could have been operating the guns and then jumping out of the helicopter to safety in one second. (00:06:01)
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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