Continuity mistake: At the beginning of Senator Kelly's campaign speech, his campaign button is predominantly white with some blue at the top and bottom. When the shot changes, the majority of the button is now blue, with only a small portion in the center being white. (00:19:20)
Factual error: When a parachuting Xavier is about to land, you can see his legs are bent at the knee to brace for landing. Since Xavier is a paraplegic, he shouldn't be able to do this. (00:19:14)
Revealing mistake: When Xavier is parachuting towards the ground, the stars in the sky are flickering on and off. (00:19:00)
Continuity mistake: When Jubilee is saying how much being a member of the X-Men means to her, one shot shows Gambit looking despondent, and the lines on his collar armor are missing. (00:10:53)
Continuity mistake: When Wolverine is telling Jubilee that she isn't going on the mission, the parts of his mask next to his cheeks are yellow, when they should be black. (00:10:41)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Mystique is walking away from Rogue, they are standing on the pavement next to the Washington Monument reflecting pool. When the shot changes, they are standing on grass. (00:19:10)
Continuity mistake: When the X-Men are flying to where Magneto is, the sclera of Gambit's eyes are colored white, when they should be black. (00:04:37)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Rogue and Mystique land next to the reflecting pool by the Washington Monument, the water is still. A couple of shots later, the water is oscillating. (00:18:36)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Bishop comes into the room where Gambit and Mystique are fighting, Gambit is between Mystique and the door. When Bishop shoots Gambit, Gambit is suddenly near the window (note the green curtain). (00:16:31)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Senator Kelly is untying the bound woman, she is in a different part of the room than she was when Kelly and Mystique first entered (note her position relative to the bookshelves). (00:15:50 - 00:16:27)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Mystique first enters the room where she plans to murder Senator Kelly, there are two bookshelves on the left, with the one closest to the camera being shorter than the one next to it. When Gambit and Mystique are getting ready to square off, the bookshelves are in the background, and they have swapped places. (00:15:52 - 00:16:15)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Mystique is leading Senator Kelly into the room to kill him, a window has appeared on the door after they enter. (00:15:40)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Mystique, disguised as Gambit, is removing the blindfold from the woman, the lines on Gambit's collar armor change length and then disappear. The lines defining Gambit's pectoral and abdominal muscles disappear as well. (00:15:55)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Wolverine has his hands draped around Blob's eyes and neck, the parts of his mask that are next to his cheeks are colored yellow, when they should be black. (00:13:33)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Wolverine is running towards Blob from behind, he is in his direct path. When the shot changes to Wolverine jumping onto him, he emerges from the right side of the screen instead of from directly behind him. (00:13:29)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Blob first confronts the X-Men, there is a light post behind him. When Rogue has her hand stuck in his chest, the light post has disappeared. (00:12:17)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Avalanche and Pyro are attacking the chambers, Avalanche destroys a bookshelf that wasn't there at the beginning of the scene. (00:10:42 - 00:11:17)
Days of Future Past: Part 2 - S1-E12
Deliberate mistake: When the crowd is protesting outside the Capitol, the same man with black hair and a brown outfit has been drawn numerous times in the shot. (00:10:23)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Gambit hands Bishop the deck of cards to cut, Bishop places them at a diagonal angle in front of him. When the shot changes, the deck is now pointing straight. (00:09:36)
Days of Future Past: Part 2 - S1-E12
Plot hole: When Gambit charges an object with kinetic energy, it makes a high-pitched sound. When he places a charged card on the arcade game to use as a trap, Wolverine should have heard it, as he possesses a superhuman sense of hearing, especially since Gambit muted the TV. (00:09:28)
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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