The Phoenix Saga (1): Sacrifice - S3-E3
Continuity mistake: When Cyclops is saying "They'll be safe in the isolation chamber " he and Jean Grey are standing near the lockers on the left side of the screen, four floor tiles away from the door. When the shot changes, the two of them have suddenly moved to the right, in line with the door, and only two floor tiles away from it. The floor tiles themselves are also now drastically smaller. (00:08:32)
The Phoenix Saga (1): Sacrifice - S3-E3
Continuity mistake: When Wolverine is breaking open the door to the space center, he leaves a long tear around the handle. When the shot changes, the tear has disappeared, and then returns in the next shot. (00:07:05)
The Phoenix Saga (1): Sacrifice - S3-E3
Continuity mistake: When Xavier is talking with Cyclops in his bedroom and turns toward the window, the back of his hover chair is pointed towards the open area immediately on Cyclops' right. When the shot changes, the back of the hoverchair is directly facing Cyclops. (00:05:09)
The Phoenix Saga (2): The Dark Shroud - S3-E4
Continuity mistake: When Xavier and Cyclops begin arguing in the hallway, the door and doorway to Jean's hospital room are visible over and behind Xavier's right shoulder, and a chart is a few feet to the right of the door. A few shots later when Cyclops is telling Xavier that he failed to warn everyone, the chart is still visible, but now the door is missing, with the wall now appearing to be longer. (00:06:40)
The Phoenix Saga (2): The Dark Shroud - S3-E4
Continuity mistake: When Cyclops and Wolverine bring Jean back above the water surface, her wet hair is pointing straight down. When the shot changes, her hair is suddenly wavy and parted over her forehead. (00:05:00)
The Phoenix Saga (1): Sacrifice - S3-E3
Continuity mistake: When the X-Men barge into the locker room, as Gambit is running towards the camera, you can see his gloves are entirely fingerless, whereas when the team first entered space center grounds, only his thumb, index finger and pinky were fingerless. (00:08:01)
The Phoenix Saga (1): Sacrifice - S3-E3
Continuity mistake: When Cyclops knocks out all the astronauts, they are in a large locker room area. Moments later when the astronauts are shown lying unconscious, the room is now a narrow corridor. (00:08:03)
The Phoenix Saga (1): Sacrifice - S3-E3
Continuity mistake: When Cyclops asks Storm to give the team cover, so they can infiltrate the space center, she is standing directly behind him, close enough to have her hand on his shoulder. When the shot changes, she is standing all by her lonesome. (00:06:11)
The Phoenix Saga (1): Sacrifice - S3-E3
Continuity mistake: When Xavier is telling the X-Men about their mission to take control of the space shuttle, some shots show Cyclops and Jean Grey seated immediately to the left of Jubilee and Wolverine, and other shots show a gap between them. (00:03:24 - 00:04:37)
The Phoenix Saga (1): Sacrifice - S3-E3
Continuity mistake: When Gambit is walking past Xavier in the War Room, the collar of Xavier's shirt is suddenly much wider than previously shown. (00:03:39)
The Phoenix Saga (1): Sacrifice - S3-E3
Continuity mistake: When Gambit announces his presence in the War Room, there is a rectangular panel on the wall to his left that is the same color as the rest of the wall. When the shot changes, the panel is now a darker gray. (00:03:41)
The Phoenix Saga (1): Sacrifice - S3-E3
Revealing mistake: During the opening battle in outer space, when the green ship uses its tail to tear a hole into the larger ship, you can see the tear slightly shift downward. (00:01:47)
Continuity mistake: When they first run away from the Spirit Drinker, Wolverine is kneeling down and cradling the unconscious Jubilee, with Gambit behind Wolverine, and Lady Deathstrike on Wolverine's left. When the shot changes, you can tell by the brown boots that Lady Deathstrike is now standing behind Wolverine instead of Gambit. (00:04:50)
Continuity mistake: When Gambit is saying "How are we gonna beat this thing when we can't even get close to it?", Jean Grey is on the viewer's left of the group and Cyclops is on her left. When the shot changes, Jean and Cyclops have swapped places. (00:16:31)
Continuity mistake: When Gambit is saying "Now what do we do?" after throwing a kinetically charged card at the Spirit Drinker, the glove on his left hand is suddenly missing. (00:07:54)
Continuity mistake: When Jubilee is saying "But the others," she is standing directly in front of Gambit. When the shot changes, she is no longer in front of Gambit. When the shot changes again, she is suddenly behind Gambit. (00:03:57)
Continuity mistake: When Leech is telling Lady Deathstrike that Callisto forced him to steal from her, she has her hand wrapped around his neck. When the shot changes, her hand is now gripping him by the chin. (00:03:00)
Continuity mistake: When Leech picks up the gun to try to defend himself from the Reavers, he is in an underground area with brick walls. When Lady Deathstrike grabs him and asks why she should spare him, they are now standing in a tunnel with walls similar to a cavern. (00:02:50)
Continuity mistake: When Beast and Xavier first enter the alien craft, Beast's black eyebrows are incorrectly colored blue for a couple of shots. (00:13:58)
Continuity mistake: When Jean tries to probe the Spirit Drinker's mind, she is standing several feet from the wall on her left. When Cyclops checks to see if she's all right, she is suddenly much closer to the wall. (00:12:07)
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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