The Dark Phoenix (2): The Inner Circle - S3-E12
Other mistake: When Wolverine lands on Leland with his claws extended, if you look closely you'll see that Wolverine's left hand ends up in Leland's chest area, yet Leland was not impaled by the claws like he should have been. (00:17:15)
The Dark Phoenix (3): The Dark Phoenix - S3-E13
Other mistake: When Professor X says "We must do all we can to defeat the Phoenix within her," there is a black spot that moves vertically across the screen as the camera is panning from Cyclops to Wolverine. It's as if there was a small bug on the lens. (00:11:00)
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)
Other mistake: When Corsair is running towards the Starjammers and Storm at the top of the Mayan structure, Lilandra can be seen among the group despite the fact that she was not in the episode before or after this moment. This was most likely supposed to instead be Jandra, the Shi'ar child that the Starjammers were trying to protect. (00:18:50)
The Juggernaut Returns - S3-E17
Other mistake: During the "Previously on X-Men..." segment before the show's intro, it shows the Juggernaut landing in the ocean and walking across the ocean floor after Gladiator had hurled him away. However, Juggernaut's fate was never actually shown after Gladiator threw him. He was only seen fading off into the distance. (00:00:50)
Weapon X, Lies, and Video Tape - S3-E19
Other mistake: The pickup truck Beast is driving appears to be missing its foot brake. (00:18:50)
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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