Have Yourself a Morlock Little Christmas - S4-E12
Other mistake: Rogue states that this is Jubilee's first Christmas as an X-Man. However, Jubilee was already a member of the X-Men when Senator Kelly declared his candidacy for President in season 1, and the season 2 premiere episode showed him being sworn-in as President. Election Day is in November and the President is sworn-in in January, so Jubilee should have already had at least one Christmas as a member of the X-Men. (00:02:00)
Have Yourself a Morlock Little Christmas - S4-E12
Other mistake: When Ape and Annalee walk to the back doors of the ambulance, the window on the right rolls down. Ignoring the fact that those windows don't actually roll down, neither Ape nor Annalee do anything to make it roll down. (00:06:55)
Have Yourself a Morlock Little Christmas - S4-E12
Other mistake: Jubilee should not have been able to see Mariana without looking around the corner. (00:10:25)
Have Yourself a Morlock Little Christmas - S4-E12
Other mistake: When Gambit is tasting the food in the crock pot, his left arm has been drawn backwards.
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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