Continuity mistake: After Jean Grey, Rogue and Wolverine locate Gambit's mini-jet, they land the Blackbird behind a row of plants. When they emerge from the Blackbird, the plants have disappeared. (00:08:55)
Continuity mistake: When the chosen one for the Thieves Guild tries to present their tithe to the External, he is shown walking right up to the tree stump where he was to have placed the tithe. When the shot changes, he is still walking forward, and therefore should've bumped into the stump. He is saying a line of dialogue as he is walking forward, so it can't be considered an action shown from a different angle. (00:06:15)
Continuity mistake: When the chosen one for the Thieves Guild is called forward to present their tithe, the chosen one for the Assassins Guild can still be seen kneeling before the External. In the next shot when the chosen one for the Thieves is shown arriving on the scene, the chosen one for the Assassins is suddenly back to standing among the other members of his guild. In the next shot, the chosen one for the Assassins is back to kneeling before the External. (00:06:00)
Other mistake: When Gambit is wiping sweat off his forehead, the locks of hair that he is rubbing his fist against do not move. (00:05:20)
Continuity mistake: During Gambit's flashback, the chosen one for the Assassin's Guild is shown to be placing their tithe box on the stump of a tree roughly halfway between the center ring and the outer edge. When the shot changes, the tithe box has suddenly moved to the center of the stump, and the tithe box itself is suddenly wider and shorter and has rotated 90°. (00:05:00)
Continuity mistake: The position of Cyclops' body changes when Jean Grey is cradling his head. At first, he is sitting slightly upright. When the shot changes, he is lying down. (00:04:40)
Continuity mistake: The amount of damage to Cyclops' uniform decreases. When his Danger Room session is first terminated, his uniform is mostly missing around his shoulders and chest. A few shots later, the aforementioned area of his uniform is not as torn up. (00:04:15 - 00:04:50)
Other mistake: When Wolverine, Rogue and Jean Grey are falling down the hole, they are all falling at the same rate, yet Wolverine lands a couple seconds after the other two. If anything, he should have landed first because he weighs more than them, especially since his bones are coated with metal, and Rogue and Jean Grey are shown to be slowing their falls by using their flight and telekinetic powers respectively. Wolverine also appears to land a couple feet in front of the hole.
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.
Other mistake: When Bella Donna is saying that Gambit was wise to leave the Thieves Guild, there is a black horizontal line on Gambit's right cheek that disappears and reappears in sync with his blinking.
Other mistake: When Rogue drops the mug of coffee onto the floor, you can see that the coffee touches her boot, yet her boot does not get any stains on it. (00:04:05)
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: In Gambit's flashback it is shown that the chosen one from the Guild of Thieves is banished to a "darkness never-ending" for breaking the covenant of the tithe. However, the same character can be seen later in the episode fighting alongside his fellow guild members.
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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