The Phoenix Saga (2): The Dark Shroud - S3-E4
Continuity mistake: When Gambit is getting ready to attack Dark Xavier, the ticket booth behind him is unoccupied. When Dark Xavier deflects Gambit's kinetically charged playing card to the ticket booth counter, a man is now inside the booth. The bottom center window also goes from being closed to being open. (00:12:16)
Savage Land, Strange Heart (1) - S3-E8
Revealing mistake: When Zaladane is helping Sauron escape, she uses her staff to reveal a hidden stairway in the floor. As Sauron descends the steps, the opening fades back into resembling the floor to suggest it is being hidden again, but Sauron fades away as well. It should be that Sauron walks out of view, and then the opening fades back into the floor. (00:02:56)
The Phoenix Saga (2): The Dark Shroud - S3-E4
Revealing mistake: When Lilandra is saying to Xavier "I have seen your face a thousand times in my mind," the edge of an animation cel is visible around the parietal area of Xavier's head. (00:20:24)
Savage Land, Strange Heart (1) - S3-E8
Audio problem: When Sauron is saying "Cowards, fools, come back," his mouth isn't moving. (00:02:02)
The Phoenix Saga (4): The Starjammers - S3-E6
Continuity mistake: When Gladiator is telling D'Ken who Corsair's prisoner is, the section of the wall directly behind the tip of the throne is green. When the shot changes, it is now the same bluish-gray color as the rest. (00:15:43)
The Phoenix Saga (3): Cry of the Banshee - S3-E5
Audio problem: When Lilandra is saying "No, for the sake of the universe, no," her mouth movement is not in sync for some of the dialogue. (00:18:23)
The Phoenix Saga (3): Cry of the Banshee - S3-E5
Continuity mistake: When Erik the Red is asking Lilandra why she won't answer him, there is a lamp in the background on the left. When the shot changes, a decorative stand has appeared next to the lamp. (00:12:00)
The Phoenix Saga (2): The Dark Shroud - S3-E4
Continuity mistake: When Xavier is looking at Moira and Banshee from his window, as the camera zooms in on the latter two, you can see they are facing each other, and Moira has her left arm on or near Banshee's hip. When the shot changes, they are standing side by side, with Moira's arms wrapped around Banshee's left arm. (00:17:41)
The Phoenix Saga (2): The Dark Shroud - S3-E4
Continuity mistake: When Lilandra first appears in Xavier's room, she appears to be around 7 feet tall. She is nowhere near that tall in subsequent shots. (00:18:29)
Savage Land, Strange Heart (1) - S3-E8
Continuity mistake: When Zaladane is first shown, she is standing several feet in front of the doorway. When the shot changes, she is now inside the doorway. (00:02:45)
Savage Land, Strange Heart (1) - S3-E8
Continuity mistake: When Kazar and his men reach the shore outside the citadel, one of the men suddenly has green skin, despite being shown with Caucasian skin tone moments before. (00:01:54 - 00:02:15)
The Phoenix Saga (5): Child of Light - S3-E7
Continuity mistake: When Lilandra is boarding her ship in the end, Cyclops and Corsair are in the background, and they are standing straight up. When the shot changes, Cyclops is now hunched. (00:19:08)
The Phoenix Saga (5): Child of Light - S3-E7
Continuity mistake: When Phoenix is telling everyone that the crystal has been sealed, Wolverine's lower half has been miscolored. His trunks and boots should be blue, but have been colored yellow, and his legs should be colored yellow, but are flesh-colored. He's also wearing his mask in this shot, but in the next shot he is not wearing it. (00:17:42)
The Phoenix Saga (5): Child of Light - S3-E7
Continuity mistake: When Phoenix is teleporting everyone out of the M'Krann Crystal, Gambit's gloves are fingerless, when it has been previously shown that the middle and ring fingers are gloved. (00:14:53)
The Phoenix Saga (5): Child of Light - S3-E7
Continuity mistake: When the action returns to the X-Men battling D'Ken, Gladiator's neck is the same blue color as his hair, when it should be grayish-purple like his face. (00:12:35)
The Phoenix Saga (5): Child of Light - S3-E7
Continuity mistake: When Gladiator is saying "All is lost, Empress," the front of Gambit's neck is flesh-colored, when it should be black like the rest of his cowl. (00:07:29)
The Phoenix Saga (5): Child of Light - S3-E7
Continuity mistake: When Storm is telecommunicating with Xavier, she is standing in front of a gray wall. When the shot changes, the wall is now green. (00:06:24)
The Phoenix Saga (4): The Starjammers - S3-E6
Continuity mistake: When D'Ken is running from the Phoenix, the M'Krann crystal has been colored roughly the same shade of gray as the pedestal it was placed on. (00:16:46)
The Phoenix Saga (4): The Starjammers - S3-E6
Audio problem: When D'Ken is ordering Gladiator to identify himself, he is speaking in a voice that sounds more like Dr. Corbeau from a few episodes earlier than it does D'Ken. (00:09:20)
The Phoenix Saga (3): Cry of the Banshee - S3-E5
Continuity mistake: When the X-Men are flying towards Cassidy Keep, Gambit's neck is flesh-colored, when it should be black from his cowl. (00:13:02)
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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