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)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Cyclops and Beast are cornering Wyngarde, Beast's entire belt is red, when normally his belt is yellow and the X in the middle has red around it. (00:16:20)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Beast says "We appear to be at the mercy of our hosts," he is noticeably further away from Cyclops than he is from the rest of the episode. The captive X-Men are chained to the floor with not much slack, so he could not have simply moved away from Cyclops on his own. (00:05:50)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: The "X" mark torn into Cyclops' shirt changes size and position a few times. (00:09:50 - 00:11:10)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Sebastian Shaw is warning the White Queen not to fail the group, the pitchfork-like pin on his jacket disappears between shots. (00:04:10)
Savage Land, Strange Heart (2) - S3-E9
Continuity mistake: When Storm breaks off communication with Beast, the animation suggests that she is removing the communicators from her chest, but they remain in place. A couple of shots later, they are completely gone. They then reappear and disappear throughout the rest of the episode. Note: this mistake may only apply to the version of the episode that appears on the DVD. In the version of the episode that appears on Disney+, Storm does indeed rip the communicators off her chest. (00:16:20)
Savage Land, Strange Heart (2) - S3-E9
Continuity mistake: The edges of the chasm that Jubilee hangs from go from being uneven to straight-lined. (00:13:40)
Savage Land, Strange Heart (2) - S3-E9
Continuity mistake: After Storm destroys the statue of Garokk, his ethereal form petrifies the surrounding area. When it changes to a wider shot, the land is back in its original state. (00:03:30)
Savage Land, Strange Heart (1) - S3-E8
Continuity mistake: At the very beginning of the episode, Sauron can be seen wearing the necklace of Garokk. Not only is he not wearing the necklace a few shots later, but he isn't even supposed to have the necklace until a few minutes later in the episode when Zaladane gives it to him after he reverts to his human form. (00:01:05 - 00:04:10)
The Phoenix Saga (4): The Starjammers - S3-E6
Continuity mistake: When Corsair first enters Cyclops' holding cell, the door says "Security Cell 3." When Corsair leaves the room, the door simply says "Security Cell." (00:09:00 - 00:13:15)
The Phoenix Saga (3): Cry of the Banshee - S3-E5
Continuity mistake: The yellow paint for the "H" marking on the helicopter pad on the roof of the Muir Island Research Center becomes smaller when the shot changes. (00:09:20)
Continuity mistake: The warning sign on the containment vessel inside the alien ship disappears in the wide shot. (00:14:40)
Continuity mistake: The three tear marks in Wolverine's uniform from when Lady Deathstrike slashes him change position several times. When she first slashes him, the tear marks appear on his chest. Other shots show the tears to be closer to his abdomen. (00:13:50 - 00:16:00)
Continuity mistake: When Wolverine is trying to get to Professor Oyama, he slashes twice at the door leaving six claw marks. When the door is shown again after Wolverine is reacting to the explosion, there are suddenly several more claw marks without him ever slashing at the door again. (00:11:40)
Continuity mistake: When Professor Oyama is telling Dr. Cornelius to begin the adamantium feed, Wolverine is reflected incorrectly in Oyama's glasses (note the device on Wolverine's left leg). (00:09:50)
Continuity mistake: Gambit's sleeves turn from black to pink when Bella Donna reveals to him that she double crossed the Thieves Guild. (00:13:25)
'Til Death Do Us Part: Part 2 - S2-E2
Continuity mistake: When Morph parks the police car outside the gates of the X-Mansion, the front half of the car is in the immediate pathway of the gate. A couple of shots later, the entire car is parked along the curb. (00:02:50)
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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