Other mistake: When the hotel clerk is checking Gambit, Storm and Jubilee into their room, he determines that they are mutants by seeing footage of Storm using her powers at the Salem Center Mall from the very first episode. While it's not unreasonable that security footage from the mall could exist showing Storm use her powers, the footage also shows an extremely close zoom-in on Storm's left eye, which is extremely unlikely, unless the security camera somehow guessed she was about to activate her mutant powers. (00:13:27)
Other mistake: When Gambit, Storm, and Jubilee get into the back of the taxi, you can see the window seat behind the driver is unoccupied, which would suggest the three of them are occupying only two of the backseats. (00:12:51)
Other mistake: When Wolverine is walking around the camp after Sabretooth attacked it, he doesn't leave any footprints in the snow, even though Sabretooth's footprints are there. (00:14:52 - 00:15:36)
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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