Continuity mistake: Cocteau's tombstone has gained a gold plate on the front of it by the end of the episode. (00:01:35 - 00:19:25)
Continuity mistake: After Wolverine carves "HERO" onto Cocteau's tombstone, he has to walk several feet away from the tombstone to get to Justine. When the shot changes, both of them are only a couple steps away from the tombstone. (00:19:15)
Continuity mistake: Wolverine's gloves have suddenly disappeared after the robot is destroyed,. (00:15:05)
Continuity mistake: The Red Skull punches Captain America's shield with his left hand, but then shows pain in his right hand. (00:13:10)
Continuity mistake: When Red Skull is leaving Wolverine and Captain America alone, he sets Captain America's shield on a table and Wolverine is shown to be hanging from stocks by his wrists with Captain America on his left and the table on his right at roughly a 45 degree angle. In a wide shot after Red Skull has left the room, the shield has vanished from the table and Wolverine is now several feet from where he originally was, with Captain America roughly at his 12 o'clock and the table roughly at his 3 o'clock. (00:10:45)
Continuity mistake: When Captain America says "Red Skull, wait!", his sleeves are entirely blue whereas they should be white from the mid-bicep and down. (00:10:45)
Continuity mistake: When the Nazis begin to surround Wolverine and Captain America, a group of them are shown to be coming through a door and into a very large room, despite the fact that the scene is actually taking place inside a narrow corridor. (00:09:50)
Continuity mistake: When Wolverine causes Cocteau to faint, his glasses fall off. When the shot changes, the glasses are nowhere to be seen on the ground. (00:09:05)
Continuity mistake: When Wolverine and Captain America first find Cocteau, the white ring on Captain America's shield is colored black in a wide shot. (00:08:45)
Continuity mistake: When Wolverine and Captain America start running, they are standing very close to each other. When the shot changes, they are several feet apart. (00:06:50)
Continuity mistake: When Wolverine is saying "You cheated me, old man!", the lower half of his trench coat briefly changes color. (00:01:40)
Continuity mistake: The restraints on the altar of sacrifice disappear after Caliban frees Jubilee. (00:17:00 - 00:19:15)
Jubilee's Fairy Tale Theater - S5-E9
Continuity mistake: When the caverns start to tremor, the book that Jubilee was holding beforehand has vanished, then reappears, and then disappears again. (00:02:00)
Continuity mistake: The amount of bandages on Beast's torso vary depending on the shot. (00:14:35 - 00:19:45)
Continuity mistake: When Arkon states that Storm is the conqueror of his heart, he is holding up a goblet with his left hand and extending his right hand towards her. Not only is the bracelet on his right hand gold when it should be silver (the bracelet on his left hand remains silver in this shot), but his right hand looks rather effeminate. Arkon and Storm were sitting right next to each other and no one was shown to be standing between them in any other shot, so the right hand in question couldn't have belonged to another person. (00:16:40)
Continuity mistake: The banner with the picture of Storm and Arkon that the workers are hanging up appears to have a transparent background, but the underside is shown to be yellow. (00:07:00)
Continuity mistake: When Wolverine is talking about Storm being worshiped by a tribe when she was a child, the portion of his mask that runs down either side of his cheeks is yellow when it should be black. (00:06:45)
Continuity mistake: In the wide shot of Arkon, Storm and the other X-Men approaching the crowd, Cyclops' face turns black. (00:18:10)
Continuity mistake: The character that says "We are saved" suddenly has gray-colored skin in the next shot. (00:18:00)
Continuity mistake: When the robot blasts Cyclops in the arm, you can see that his uniform tears. The tear has instantly mended itself in the next shot. (00:13:10)
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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