Continuity mistake: When Gambit first walks into Bobby's cell, Bobby is sitting in a chair up against the back wall. A few shots later, Bobby is sitting in the center of the cell. (00:09:55)
Continuity mistake: The cell that Bobby was held captive in is noticeably smaller after he is set free. (00:09:55 - 00:11:40)
Continuity mistake: When Gambit is saying "You got me in the guild, Bobby," you can see on the wall across the hall that there is a switch that is the same red color as the wall. A few shots later, the switch is now gray. (00:10:18)
Continuity mistake: Bella Donna's engagement/wedding ring from Gambit doesn't appear on her finger until she mentions that she still wears it. (00:10:55)
Continuity mistake: When Bobby starts walking out of his cell, Gambit has his back to him. When the shot changes, Gambit is suddenly facing him. (00:11:15)
Continuity mistake: After Bobby is set free, Gambit, Bella Donna and her henchman remain in Bobby's cell. When Bella Donna begins torturing Gambit, the two of them are suddenly alone in the cell. (00:11:20)
Continuity mistake: When Bobby and Pierre enter the basement of the Thieves Guild's mansion, Bobby is on the left, and Pierre is on the right. When the shot changes, they have swapped places. (00:12:43)
Continuity mistake: When Gambit is looking at himself in the mirror while wearing a tuxedo, you can see in his reflection that he is barehanded. In the next shot when he removes the tuxedo, he is wearing his usual black gloves. Also, the rose on the tuxedo goes from being on his right side (reflection's left) to being on his left side just before he removes the tuxedo. (00:13:15)
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)
Continuity mistake: When Bella Donna is saying the Assassins are prepared for the tithe, a man with long green hair is behind her on her left. When the shot changes, he appears to be standing between her and Gambit. When the shot changes again and Bella Donna is stroking Gambit's hair, he is nowhere to be seen. (00:14:16)
Continuity mistake: When Gambit pushes Bella Donna over, she is on his left, and there is a tree stump on his right (out of shot). When the shot changes, she is up against the tree stump. (00:14:25)
Continuity mistake: When Pierre is telling the Assassins that they betrayed the Thieves, he raises his left arm and points his finger at them, and then lowers his arm back down. When the shot changes, his left arm is raised again. (00:15:00)
Continuity mistake: When the Thieves and Assassins guilds begin to skirmish, they start by trying to regain the weapons that Jean Grey telekinetically confiscated from them. A couple seconds into the fight and most of the weapons have disappeared altogether. (00:15:20)
Continuity mistake: When Rogue flies back towards Gambit and Bella Donna, Bella Donna is standing behind Gambit. When the shot changes, Bella Donna is standing in front of Gambit. (00:15:35)
Continuity mistake: When the External is emerging from the water, the Thieves Guild's tithe box is missing from its respective tree stump. In the next shot, it is back in place. (00:16:30)
Continuity mistake: When the External states the Guild of Thieves have dishonored the tithe, both the Thieves' and Assassins' tithe boxes are missing from their respective tree stumps. (00:17:10)
Continuity mistake: When Gambit places Bella Donna's ring on the ground, she is nowhere around it. When the shot changes, the ring is suddenly right next to her. Note: this mistake may only apply to the DVD version of the episode, as the version of the episode on Disney+ does have Bella Donna there when Gambit sets the ring down. (00:18:50)
Continuity mistake: The size of the hole beneath the trap door in the Thieves Guild's mansion changes. When Wolverine, Rogue and Jean Grey are shown falling down it, it is easily large enough for the three of them to fall down without bumping into each other. When we see the hole in the ceiling after Rogue destroys the wall that was falling on her, the hole is barely large enough for one person to fit through. The hole also moves closer to the back corner of the room, whereas it appeared to be closer to the back-center of the room once they landed.
Continuity mistake: The orientation of Gambit's mini-jet respective to the Blackbird changes. When the Blackbird first lands, the mini-jet is perpendicular to it. When Wolverine, Rogue and Jean Grey go over to inspect the mini-jet, it is suddenly parallel to the Blackbird.
Continuity mistake: Shortly after Wolverine, Rogue and Jean Grey enter the Thieves Guild's mansion, they fall down a trap door. However, the trap door is not there when they first enter the mansion, instead only appearing in the shot where they step on it.
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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