The Phalanx Covenant: Part 1 - S5-E1
Continuity mistake: When Mr. Sinister blasts the Phalanx-civilians, his gloves are red. A couple of shots later, his gloves are their usual blue. (00:17:50)
The Phalanx Covenant: Part 1 - S5-E1
Continuity mistake: When Beast says "And we waited until you arrived," his eyebrows keep changing from blue to black. (00:16:10)
The Phalanx Covenant: Part 1 - S5-E1
Continuity mistake: When Beast replays the video of Warlock's tissue sample assimilating the metal, the human and mutant tissue samples on the left have disappeared. (00:11:35 - 00:12:30)
The Phalanx Covenant: Part 1 - S5-E1
Other mistake: As usual, Wolverine's jeep is missing its windshield. (00:08:25)
The Phalanx Covenant: Part 1 - S5-E1
Continuity mistake: When Beast is running from the Phalanx through the mansion's hallways, his trunks go from being Speedo-like to resembling basketball shorts. (00:06:50)
The Phalanx Covenant: Part 1 - S5-E1
Continuity mistake: When Wolverine confronts Sabretooth in his holding cell, Wolverine's face is colored yellow. (00:04:25)
The Phalanx Covenant: Part 1 - S5-E1
Continuity mistake: When Jubilee accidentally lets slip that Sabretooth is in the mansion in front of Wolverine, the hand portions of her gloves disappear. (00:03:00)
Family Ties - S4-E17
Continuity mistake: When the mutated Wolverine picks up and throws Xavier, before Beast comes to aid him there is nothing immediately around Xavier but the ground. When the shot changes, Xavier and Beast are suddenly next to a cliff wall. (00:17:55)
Family Ties - S4-E17
Continuity mistake: At various points in the episode, the High Evolutionary's "teeth" go from being white to being the same purple color as his face. (00:05:45 - 00:13:40)
Family Ties - S4-E17
Continuity mistake: After Magneto and Wolverine have been captured, when Wolverine is asking Magneto what is going on, the perspective of the shot makes it look like Magneto is looking down on Wolverine from a considerably taller height when they are both standing on a level floor. Additionally, the square slabs that make up the floor become smaller. (00:12:35)
Family Ties - S4-E17
Continuity mistake: For the first half of this episode, Magneto is wearing a red dress-shirt with a black tie under a dark gray trenchcoat. After he is captured by the High Evolutionary, he is suddenly wearing his usual red and purple costume. Even if Magneto brought a change of clothes with him, it's extremely unlikely that the High Evolutionary would change his clothes for him. (00:03:40 - 00:12:40)
Family Ties - S4-E17
Continuity mistake: The style of the lettering on Magda's gravestone changes after the goat-woman runs away from Magneto. There is also a stone that was next to the grave when it is first shown that has suddenly disappeared in the same shot of the goat-woman running away. (00:09:10 - 00:09:45)
Family Ties - S4-E17
Continuity mistake: Quicksilver's neck is colored the same light-blue hue as his uniform when he says "The mutant who did this..." (00:07:45)
Family Ties - S4-E17
Continuity mistake: When Scarlet Witch and Quicksilver first meet the High Evolutionary, Scarlet Witch's headgear alternates between being red and pink. (00:05:55)
Family Ties - S4-E17
Continuity mistake: When Bova is bringing the baby twins to Django and Marya's house, the arm she is carrying the respective twin in changes depending on the shot. When she is first shown walking towards the house, she is holding Wanda in her left arm and Pietro in her right. When she is walking up the steps to the door, she is carrying Pietro in her left arm and Wanda in her right. When the shot changes after Django opens the door, the twins have switched arms again, and then again when she hands the babies to Django and Marya. (00:02:30)
Continuity mistake: When Xavier is explaining to Wolverine the importance of vigilance, Beast can be seen directly behind him. When the shot changes, Beast is no longer standing behind Xavier. (00:18:25)
Secrets, Not Long Buried - S4-E15
Continuity mistake: The mutants that have gathered for Solarr's speech are in different places throughout depending on the shot. (00:16:50 - 00:18:50)
Continuity mistake: The Colony's Acanti ship goes from having its face buried into the walls of the chasm and its body above ground to having its body partially buried in the valley floor and its face free from the wall. (00:06:50 - 00:08:10)
Revealing mistake: Wolverine's nipples literally disappear from his chest when he says "Do I feel lousy." (00:07:15)
Continuity mistake: Rogue's vanity has a teddy bear and a telephone on it. When Gambit comes into her room, the phone has disappeared. (00:03:55)
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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