Continuity mistake: When Beast presses the button to listen in on Omega Red, Storm and Wolverine, Rogue's arm is flesh-colored whereas it should be green since she is wearing her uniform. (00:13:35)
Continuity mistake: The mini-sub that Storm docked onto the hull of the nuclear submarine disappears and reappears throughout the rest of the episode. (00:07:20 - 00:17:45)
Other mistake: After Omega Red stabilizes the nuclear sub while it is moving, the military somehow has a live video feed from outside the sub despite the fact that they didn't send any other submarines out to monitor the mission. (00:09:00)
Audio problem: When Wolverine says "In a toxic nuclear powder keg," his mouth is not moving. (00:08:10)
Continuity mistake: When Storm says to Wolverine "You know small spaces overwhelm me," you can see that her lightning bolt earrings are suddenly missing. (00:06:30)
Continuity mistake: The number of "rows" on the purple devices on Omega Red's face varies throughout the episode, sometimes even changing quantity in the same shot.
Continuity mistake: When Wolverine says "Who do these genius spy-catchers think they're dealing with, Winnie the Pooh?!" his tongue is flesh-colored instead of being a normal reddish hue. (00:04:30)
Continuity mistake: When Wolverine says "For a boy scout! Omega Red eats the stuff for breakfast!" his normally-red belt is yellow, goes back to being red a couple of shots later, and then is yellow again a couple of shots after that. (00:04:45)
Character mistake: The Colonel states that Hilo, Hawaii is about 120 miles from Pearl Harbor. It is actually more than 200 miles. (00:03:25)
Factual error: When Omega Red is shown a photograph of Hawaii, the island of Niihau is missing, and Kauai is too close to Oahu. (00:03:15)
Continuity mistake: When the colonel is talking to Omega Red on the giant monitor, he is standing in different spots throughout the scene depending on the shot. (00:02:45 - 00:04:10)
Continuity mistake: When Omega Red was frozen at the end of the season 2 episode "Red Dawn", his mouth was open. When the military discovers him at the beginning of this episode, his mouth is closed. (00:02:30)
The Phalanx Covenant: Part 2 - S5-E2
Continuity mistake: The final shot of the episode shows Jubilee among the group of X-Men. However, she was not present in the group shots that preceded this one. (00:20:40)
The Phalanx Covenant: Part 2 - S5-E2
Continuity mistake: When the group is standing together in a circle at the end, Xavier is sort of in the center of the circle and Rogue and Storm are several feet to his right. When the shot changes, Rogue and Storm are suddenly right next to Xavier. (00:19:25)
The Phalanx Covenant: Part 2 - S5-E2
Continuity mistake: When Jean Grey hugs Cyclops, her hands are colored blue. (00:19:25)
The Phalanx Covenant: Part 2 - S5-E2
Continuity mistake: When Xavier and the others are approaching Cyclops, Storm, Rogue and Wolverine, Magneto is shown wearing his helmet and Gambit is shown wearing his trenchcoat. When it changes to an overhead shot of the group, Magneto is no longer wearing his helmet and Gambit is no longer wearing his trenchcoat and his normally-black headgear is colored blue. (00:19:20)
The Phalanx Covenant: Part 2 - S5-E2
Continuity mistake: When Beast says to Warlock "We are at your disposal," Magneto is suddenly clean-shaven. (00:16:35)
The Phalanx Covenant: Part 2 - S5-E2
Other mistake: When Forge says "Now we need offensive power," he opens up a containment bubble with no one inside it. The bubbles are transparent, so he would have known whether or not someone was inside it and it would make no sense for him to open up an empty bubble since he was in need of reinforcements. (00:15:55)
The Phalanx Covenant: Part 2 - S5-E2
Revealing mistake: When Forge says "That's where we'll begin our assault," his mustache disappears from his face. (00:14:50)
The Phalanx Covenant: Part 2 - S5-E2
Revealing mistake: The shot of Cameron Hodge glaring at Xavier after Xavier asks him about his lack of humanity is a recycled shot from the previous episode. (00:14:30)
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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