Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Professor X, Cyclops and Jean Grey enter the room where Senator Kelly was abducted, Cyclops goes over to inspect the hole in the wall and Professor X states that his watch has stopped working. Cyclops, still on the other side of the room, asks why that's important. When Professor X drops his watch and it clings to his hover-chair to demonstrate that it's been magnetized, Cyclops is suddenly behind Professor X. (00:20:30)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Gambit is telling Rogue that he'll park her car, the pink stripes that are normally on his pants are missing. (00:02:40)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Rogue punches the Blob, her arm is shown to be sinking into the middle of his chest. When the shot changes, her arm is suddenly in his stomach. (00:12:25)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Gambit is jumping onto the tree branch, the first shot shows that he is jumping towards the right side of the tree. When the shot changes to him landing on the branch, it is suddenly on the left side of the tree. (00:12:00)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: The final scene from the previous episode is reprised in the beginning of this episode, yet some of the dialogue is different or omitted altogether. In Part 1, when Storm says "We all have dark sides to our souls," Wolverine responds by telling her to speak for herself and states he's more suspicious of Bishop than anybody. Also, when Rogue walks in and asks who Bishop is, before anyone can tell her, Gambit announces his arrival. When Bishop accuses Gambit of being the traitor, Gambit tells him he thinks there's been a mistake. In this episode, Wolverine never states that he is suspicious of Bishop, Professor X tells Rogue who Bishop is before Gambit walks in, and when Bishop accuses Gambit of being the traitor, he fires his gun at him before Gambit can even say anything.
Days of Future Past: Part 1 - S1-E11
Continuity mistake: When Wolverine is telling Bishop that he's not letting him out of his sight, the tubes on the back of his right hand are missing, and then are there in the next shot. (00:17:20)
Days of Future Past: Part 1 - S1-E11
Continuity mistake: When Jean Grey is inspecting Bishop's gear, she isn't wearing any lipstick. A couple of shots later, she is suddenly wearing lipstick. (00:15:05)
Days of Future Past: Part 1 - S1-E11
Continuity mistake: Bishop's goatee is the same color as his flesh when he is first shown sitting down in the War Room. (00:14:55)
Days of Future Past: Part 1 - S1-E11
Audio problem: When Beast says to Gambit "Though I am always in haste, I am never in a hurry," his mouth is completely closed for most of the line. (00:11:30)
The Unstoppable Juggernaut - S1-E8
Continuity mistake: The windshield from Wolverine's jeep is missing when he pulls up to the bank. (00:08:45)
Continuity mistake: When Gambit and Wolverine are about to fight each other, Wolverine's claws are extended, and Gambit has a kinetically charged playing card raised in his right hand. When Rogue intervenes, Wolverine's claws are suddenly retracted, his hands are incorrectly colored white, and Gambit's right arm is down at his side, not holding any card. A couple of shots later, Wolverine's claws are once again extended. (00:07:15)
Continuity mistake: When Jubilee blasts Sabretooth through walls of the War Room and outside, it is shown to be on the mansion's ground level. Many other episodes however depict the War Room to be in the underground levels of the mansion, specifically in the episode "The Unstoppable Juggernaut" where the War Room is still intact after the mansion is destroyed from the ground up.
The Unstoppable Juggernaut - S1-E8
Continuity mistake: When Storm, Rogue and Jubilee are out driving and looking for Wolverine, Rogue's headband is the same color as her flesh. (00:04:45)
The Unstoppable Juggernaut - S1-E8
Continuity mistake: When the team arrives at the destroyed mansion at the end of the previous episode, Cyclops' seat is blue, Rogue says "It can't be" while raising her right hand up to her mouth in disbelief, and Wolverine is growling and extending his claws. When the team is shown arriving at the destroyed mansion at the beginning of this episode, Cyclops' seat is now light-red, Rogue says "It can't be" while her arms remain at her sides, and a silent Wolverine is casually putting on his mask and walking towards the exit ramp of the Blackbird. (00:02:23)
Slave Island - S1-E7
Continuity mistake: When Cameron Hodge is telling Gyrich and Trask about Cable, the books on the table move closer to Hodge between shots. (00:13:10)
Revealing mistake: When Wolverine, Storm, Rogue and Gambit are walking down the stairs to the subway station, you can see that they aren't actually descending the steps, but walking on thin air. (00:11:10)
Audio problem: When Callisto says to Cyclops "away from those who fear us," her mouth is completely closed. (00:09:20)
Continuity mistake: When Gambit is avoiding the electrified coils in the Danger Room, his normally black and red eyes are colored like a normal person and his gloves are entirely fingerless whereas they are usually only fingerless for the thumb, index and pinkie fingers. (00:02:15)
Continuity mistake: When Storm is having a flashback to her childhood in a fit of claustrophobia, she is depicted as a Caucasian girl with red hair. (00:03:35)
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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