Audio problem: When Professor X says "I was wrong Wolverine. I should have listened to you," his mouth is completely closed. (00:19:50)
Continuity mistake: When Sabretooth tells Jubilee that her powers are useless if she can't use her hands, the glove on her left hand turns from yellow to brown multiple times. (00:15:50)
Continuity mistake: When Sabretooth is sitting in the hover chair in the War Room, the chair is shown to be hovering up and down in the wide shot, but when a closeup of Sabretooth is shown, the background behind him remains stationary, indicating the chair is also stationary. (00:04:35)
Continuity mistake: When Wolverine says to Sabretooth "Be careful what you ask for," his arms are yellow. (00:17:05)
Continuity mistake: The stains from the tomatoes that are thrown at Beast disappear from his jumpsuit. (00:10:05 - 00:10:55)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When Rogue goes to touch Wolverine with her bare hand to stop him, she is shown removing the glove from her right hand. After Wolverine collapses, Rogue is now missing the glove from her left hand, and her entire left arm, including the hand, is solid green. (00:11:55)
Night of the Sentinels: Part 2 - S1-E2
Other mistake: After Storm and Cyclops fly away from the barrage of Sentinels, one Sentinel is shown to have his right foot "floating" on top of the left foot of another Sentinel, almost as if their feet were occupying the same space. (00:11:25)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When Rogue catches the security guard from the collapsing tower, he has black hair. When she is flying through the air with him as well as when she dumps him in the grass, his hair is red-orange. (00:06:50)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When Wolverine is playing pool, he scratches the cue ball and the cue ball is then back on the table without him retrieving it. (00:13:35)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: Immediately after Storm, Wolverine, Beast and Morph exit the Mutant Registration Center, Beast and Wolverine are shown to be running alongside Gambit and Cyclops. However, mere moments later, Gambit is shown to be blowing up a security fence so Storm, Wolverine, Beast and Morph can rendezvous with Gambit, Cyclops and Rogue. (00:06:45 - 00:07:20)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: After Cyclops tells Gambit to blow up the fence and Rogue flies into frame, her headband and the patches on her uniform that are all normally black are now red. Additionally, the black encircled X on a red background on the left side of her chest is now a yellow X on a red background. (00:06:35)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When Gambit says "You wanna play with Gambit? Here, take a card!" the glove on his right hand is missing, then is suddenly back on his hand when he says "House wins." (00:05:50)
Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: The Sentinel that is intercepting Jubilee when she is running back home to check on her foster parents is initially following her along the sidewalk from behind, but suddenly catches up to her in a perpendicular path from the street. There are only two Sentinels shown in this scene and the other one caught her from the front as it turned a corner, so it couldn't have been a different one. (00:14:40)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: At the end of the previous episode, Rogue says to Cyclops "You look nervous as a long-tailed cat in a room full of rocking chairs," to which he responds, "I just wish I knew what was happening in there." Cyclops then immediately looks to his right and sees military vehicles approaching and says "We've got trouble." At the beginning of this episode, the same scene is shown again, only this time Gambit says "If that was me in there you wouldn't have to worry" before the military vehicles are shown to be arriving.
Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: The position of the police cars around Sabretooth change from shot to shot. (00:01:15)
The Unstoppable Juggernaut - S1-E8
Continuity mistake: Gambit is the central character in the previous episode "Slave Island", and is on the Blackbird with the rest of the team when they arrive at the destroyed X-Mansion. However, the very next episode begins where "Slave Island" left off, and Gambit is conspicuously missing from the episode.
Other mistake: When Rogue is hovering above Muir Island, she pulls out a book to confirm she's in the right place, and the picture of Muir Island in her book shows it to have three smaller islands on its south side. When she lowers the book to look at the actual island, only the large island shown on the southwest side in the book is there. She's only hovering a few hundred feet above the island, so even though the other two islands were small, they should still be visible. (00:09:48)
Other mistake: When Rogue begins flying towards Cable after disarming him, she is only about 30 feet away from him. As she is flying towards him, he takes the time to pull a plasma grenade from his belt, pull out the pin with his mouth, and then throw it at her. In the time it took him to do all of that and given the speed at which Rogue was flying towards him, she should reach him well before he could throw the grenade at her. (00:18:05)
Other mistake: When Gambit, Storm, and Jubilee get into the back of the taxi, you can see the window seat behind the driver is unoccupied, which would suggest the three of them are occupying only two of the backseats. (00:12:51)
Other mistake: When Wolverine is walking around the camp after Sabretooth attacked it, he doesn't leave any footprints in the snow, even though Sabretooth's footprints are there. (00:14:52 - 00:15:36)
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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