Days of Future Past: Part 2 - S1-E12
Continuity mistake: When Mystique starts walking away from Rogue, her footsteps are audible, and she takes about four steps. When the shot changes to a closeup of Rogue asking why Mystique tried to turn her into one of Apocalypse's slaves, if you listen carefully, you can hear Mystique take about ten more steps. When the shot changes again, Mystique is suddenly only a couple steps away from Rogue. (00:18:58)
Continuity mistake: When Jean is using her telekinetic powers to rescue Senator Kelly from Master Mold's lab, she drops him on the floor in the middle of the lab. When Cyclops gets blasted by Master Mold after he and Jean run to grab Kelly, Jean and Kelly are suddenly inside the mine shaft. A couple of shots later, Jean and Kelly are now standing at Master Mold's feet. (00:15:42)
Continuity mistake: When Omega Red is at the podium and gloating about the rebirth of the Soviet Union, the hammer and sickle emblem on the podium is the same color as the rest of the podium. When he destroys the podium, the hammer and sickle is now red on a blue background. (00:15:08)
Continuity mistake: When Omega Red ties up the parliament member with his coils, there is a space of about two feet between the man and Omega Red's wrist. When Omega Red begins siphoning the man's life force and reeling him closer, there is suddenly more distance between the two. (00:09:24)
'Til Death Do Us Part: Part 1 - S2-E1
Continuity mistake: When Morph is looking at the mansion through a pair of binoculars, the binoculars have two lenses. When the mansion is shown from the binoculars' point of view, there is only one lens. (00:13:43)
Continuity mistake: When Gambit is asking Xavier why the X-Men must all die to save Senator Kelly, the top of Wolverine's mask is incorrectly colored blue. A few shots later, this portion of the mask is correctly colored yellow, but then the portion of his mask by his right cheek is also yellow, when it should be black. (00:09:48)
Days of Future Past: Part 2 - S1-E12
Continuity mistake: After Blob knocks Cyclops to the ground, Jean helps him up, and the two of them are standing a step away from Blob. The shot changes to Blob pointing and laughing for roughly a second, and when the shot changes again, Cyclops and Jean have disappeared, with not enough time to have moved offscreen. (00:12:20)
Continuity mistake: In the flashback of Shadow King terrorizing a young Storm, in one shot she is shown sitting on the palm of his left hand. When the shot changes, she is now on the palm of his right hand. (00:15:18)
Continuity mistake: When Rogue is saying that Xavier could barely handle the Shadow King, Storm is looking over her right shoulder. When the shot changes, she is looking forward. (00:09:47)
Continuity mistake: When Morph is wiping down the bar, he is wiping from left to right. When the shot changes, he is wiping up and down. (00:07:09)
Continuity mistake: When the riverboat captain is talking about how Wolverine is looking for Morph, Wolverine is standing several feet away looking over the side of the boat. When the shot changes, Wolverine's left arm is suddenly behind the captain's back, offering his monkey a peanut. (00:04:41)
'Til Death Do Us Part: Part 2 - S2-E2
Continuity mistake: When Wolverine is saying it's time for the big game, the pink stripes on Gambit's right leg are on the inside of the leg, when they should be on the outside. (00:17:30)
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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