Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: When Jubilee is trying to gain entry to the Danger Room, she is pressing random buttons that light up. When the shot changes, some of the lit up buttons are not ones she pressed, and some of the ones she pressed are no longer lit up. (00:10:34)
Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: When Gambit and Wolverine are sparring in the Danger Room, at one point Gambit dives onto a piston and then rolls off moments before it smashes him into another piston, with a piece of the bottom right of his trenchcoat being torn off in the process. When Jubilee is explaining to everyone that she was trying to help Gambit, his trenchcoat is now untorn. (00:11:07 - 00:11:43)
Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: When Jubilee blasts Wolverine across the Danger Room, Gambit is shown lying flat on the ground. When the shot changes, he is now resting on his elbows. (00:11:30)
Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: When Jubilee is saying "That's a nice way of saying 'mutants'," the black horizontal line on her left earring briefly turns the same red color as the rest of the earring. (00:12:59)
Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: When the Sentinel is resting against the building while lying in wait for Jubilee, the building itself has a solid exterior with the occasional window. When the shot changes, it is now a glass building. Additionally, when the Sentinel was resting against the building, its entire body was obscured, but when the shot changes, part of the right side of its body was sticking out. (00:14:35)
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 1 - S1-E1
Continuity mistake: When the civilian slams on his brakes to avoid hitting the Sentinel, you can see he is wearing sunglasses, but within the same shot, the dark lenses turn into clear lenses. (00:14:59)
Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: When Gambit is saying he could easily break into the Mutant Registration Center by himself, Morph is wearing yellow gloves. When Morph suggests going into the building disguised as Gambit, his hands are suddenly bare. (00:15:45)
Night of the Sentinels: Part 1 - S1-E1
Audio problem: When Cyclops is saying "Okay Storm, do your thing," his mouth movement does not match the dialogue. (00:18:31)
Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: When Beast tosses Wolverine over the fence, Wolverine's bare arms are the same yellow color as his costume. (00:19:12)
Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: When the guard orders Wolverine, Beast and Morph to halt, Wolverine and Morph are standing next to each other, with Beast behind and between them. When the shot changes, Morph is now behind Wolverine to his left, and Beast is behind Morph and to his left. (00:19:19)
Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: When Beast is first approaching the security lockbox, the word "Security" takes up the entire width of the front panel. When the shot changes, there is now more spacing on either side of the word. (00:20:17)
Night of the Sentinels: Part 1 - S1-E1
Continuity mistake: When Wolverine, Storm and Morph are approaching the door after Beast has disabled the electronic beams, the door handle is pointed at 6 o'clock. When Storm grasps the handle, it is pointed at 5 o'clock. (00:20:38)
Night of the Sentinels: Part 1 - S1-E1
Plot hole: Wolverine bails out on the mission to destroy the files at the Mutant Registration Center to instead go look for Jubilee after she goes missing. When the rest of the team arrives, Wolverine is already there waiting for them. They flew to the Mutant Registration Center in a jet and their mission briefing heavily implied that they needed to leave immediately, so there is no way Wolverine could have arrived before them if he was off looking for Jubilee first.
Night of the Sentinels: Part 1 - S1-E1
Other mistake: In the scene where Professor X uses his psychic powers to deduce that Jubilee is trying to escape the mansion, there is a semi-dissolve edit that simultaneously shows a close-up of Professor X with his left hand on his forehead and a counterpart image of Jubilee hiding around the corner. If you look closely at Professor X in the counterpart image of Jubilee, his left arm and hand are shown to be on his hover-chair's armrest and not his forehead.
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When Beast is leaping through the corridor, the black X with the black rectangular border on a red background on his waistband briefly becomes a red rectangle on a yellow background with no X. (00:02:37)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When the guards are waiting to ambush the heroes, all of them have red hair. When Storm blows them all away with a gust of wind, one of them now has black hair. (00:02:45)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When Wolverine shuts the door Strom is opening, the handle is pointed at 6 o'clock. When he starts sniffing the guards' gun oil, the handle is now pointed at 7 o'clock. Wolverine's hand also goes from being under the handle, to the center of the door. (00:02:50)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: At the beginning of the scene where Morph is impersonating a commanding officer, a guard is shown with a golden-brown colored name tag that turns green as he moves towards the camera, and the writing disappears. (00:03:29)
Night of the Sentinels: Part 2 - S1-E2
Continuity mistake: When Morph fools the guards into going into a different room, you can see him transform back into his regular self in silhouette, and his jacket suddenly goes down below his knees, similar to Gambit's, whereas Morph's jacket stops at his waist. (00:03:44)
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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