Other mistake: When Wolverine is leaving to find Yuriko and Jubilee offers to tag along, the camera is fluttering in and out of focus for a few seconds. (00:07:01)
Other mistake: When Wolverine first enters the subway, there are two tracks, and there is a train moving away from the camera on the track closest to the platform. When Gambit and Jubilee enter the same area moments later, there is now a train on the same set of tracks, but moving towards the camera. (00:07:38 - 00:08:07)
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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