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)
Character mistake: When Beast discovers that Iceman has escaped from the containment device, he takes several steps in the room before he even realizes that Iceman is gone. The device was not obscured by anything, so Beast should have realized as soon as he entered the room that Iceman was gone. (00:11:30)
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)
Other mistake: When Cyclops blasts Iceman with his optic beam, the image of Wolverine encased in ice remains on-screen, when it looks as if the shot was supposed to completely change to Iceman getting knocked back by the blast. (00:05:35)
Character mistake: When the two security guards are arguing over whether heat or humidity is worse, one guard says "It's midnight, and it's still 97°." However, moments before that the same security guard checked the temperature on his computer and it indicated it was 85°.
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
Revealing mistake: When the X-Men are being beamed down to the Moon, Rogue's mouth is missing. (00:08:50)
The Dark Phoenix (4): The Fate of the Phoenix - S3-E14
Revealing mistake: In what appears to be an animation error, when Cyclops shoots his optic beam after he and Jean emerge from hiding, his bandolier is absorbed into his uniform. (00:14:25)
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
Audio problem: When Lilandra is consulting the Supreme Intelligence of the Kree, his mouth movement is out of sync with his dialogue. (00:04:30)
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)
The Dark Phoenix (4): The Fate of the Phoenix - S3-E14
Continuity mistake: After Storm rescues Gambit from falling to his death and they fly outside, when the shot changes they have literally appeared out of thin air. (00:10:30)
The Dark Phoenix (4): The Fate of the Phoenix - S3-E14
Audio problem: When Cyclops says "Then why not trust us to deal with Jean?" his mouth is completely closed. (00:03:10)
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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