Continuity mistake: After Storm is caught in a net and uses a lightning bolt to burn a hole in it, the net has magically disappeared altogether in the next shot. (00:14:30)
Continuity mistake: When Cyclops is telling Raknar that he hasn't agreed to anything, the back of Raknar's head is flesh-colored when it is shown to be black throughout the episode. (00:14:00)
Continuity mistake: Corsair's normally brown eyebrows and mustache are suddenly black when Cyclops is asking him if he would have come back for him and his brother had he known they were alive. (00:11:10)
Continuity mistake: Cyclops' gloves disappear when he jumps off the pier. (00:04:10)
Continuity mistake: The airplane passenger reading the newspaper goes from being in an aisle seat to a window seat. (00:02:15)
Continuity mistake: When Professor X is apologizing to Iceman, there is a red contour line on the side of his hoverchair that wasn't there before. (00:18:05)
Continuity mistake: Iceman's ice form alternates between being transparent and solid throughout the episode.
Continuity mistake: Strong Guy completely disappears from the screen after the water tower falls on him. (00:17:25)
Continuity mistake: Havok goes from being completely buried under boxes to be only buried up to his waist. (00:16:55)
Continuity mistake: When Lorna discovers Havok half-buried under the boxes, the shirt he was previously seen wearing under his jacket is missing. (00:17:55)
Continuity mistake: Throughout the episode, the graphic on Jubilee's shirt alternates between being an X in a circle and a circle with a horizontal line going through the center.
Continuity mistake: Jubilee's earrings disappear when she insists on helping Iceman inside the compound. (00:11:55)
Continuity mistake: When Iceman steps onto the containment field platform, Professor X moves over right next to him, hovering over the platform himself. When Professor X activates the containment field to trap Iceman in place, Professor X is suddenly away from the platform. (00:07:45)
Continuity mistake: When Iceman is saying to Professor X "You can't tell me what to feel...", Professor X's tie is solid blue when it is supposed to be blue and black striped. His suit is also missing the breast pocket and handkerchief. (00:07:35)
Continuity mistake: When Beast is hanging upside down from the light, his belt is blue when it should be yellow. (00:05:00)
The Dark Phoenix (4): The Fate of the Phoenix - S3-E14
Continuity mistake: Lilandra's adviser goes from having no tattoo-like markings around his eyes to suddenly having them in a later scene. (00:09:00 - 00:13:20)
The Dark Phoenix (4): The Fate of the Phoenix - S3-E14
Continuity mistake: When Professor X and Lilandra are having their psychic meeting, Lilandra's dress changes from blue to red. (00:05:55)
The Dark Phoenix (4): The Fate of the Phoenix - S3-E14
Continuity mistake: When Cyclops is talking to Rogue, his abdominal muscles go from being a 4-pack to a 6-pack. (00:06:50)
The Dark Phoenix (4): The Fate of the Phoenix - S3-E14
Continuity mistake: Professor X's usual hoverchair was destroyed by the Dark Phoenix in the previous episode, so the Shi'ar gave him a new one to use on their starship. However, when Professor X is lamenting over the X-Men's imminent defeat against the Shi'ar Imperial Guard, he is back in his original hoverchair. Towards the end of the episode, he is back in the Shi'ar hoverchair. (00:04:10 - 00:13:15)
The Dark Phoenix (4): The Fate of the Phoenix - S3-E14
Continuity mistake: When Gambit says to Wolverine "Gambit will be ready," his pants are light-blue colored. A couple of shots later, they are back to being their usual black. (00:05:30)
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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