Slave Island - S1-E7
Plot hole: After Storm's attempt to escape the Genoshan prison is thwarted, she ends up in the ocean right at the shoreline of the beach, where she is captured by a Sentinel. Aside from the fact that it makes no sense for a Sentinel to be hiding in the ocean in the event that a mutant tries to escape the prison, there is absolutely no way that a two-story tall robot could hide in the ocean right by the beach, as the water would be way too shallow. You can even see that the water level only goes up to the Sentinel's ankle area when it is standing upright in the ocean. (00:03:15)
Suggested correction: Perception. (1) The Sentinel isn't as close as it appears. If it were close, then she would have been caught in its waves as it emerges. Also, she would be looking only at its chest circle. It's several yards away. (2) She washes ashore. She fell from the sky. She couldn't have fallen from that great height into shallow water without hitting bottom. (3) It's also a two-story tall robot. Its weight would sink it into the sand. So it could have very well been down that deep.
Sentinel never sank into sand in other episodes.
Well, it's shown here.
Days of Future Past: Part 2 - S1-E12
Factual error: When Gambit is inside his mini-jet after escaping from Bishop and Wolverine, his radar screen says "Washington D.C." but the graphic above it is Washington state.
Days of Future Past: Part 2 - S1-E12
Revealing mistake: When Gambit draws a card from his sleeve to use as a trap, the gloved part of his hand that is below the pocket is translucent. (00:09:28)
Continuity mistake: When Rogue is flying toward Adler's lab, you can see the building is several stories off the ground. When she flies in through the hole in the roof, the interior of the lab is on the top-level, whereas the previous episode showed that the lab was on the ground level. (00:12:55)
Continuity mistake: When the three horsemen are climbing onto their mechanical horses, Famine's horse is in the middle, and Pestilence's horse is on the right. Once all three have all been individually shown to be mounting their horses, Famine and Pestilence have swapped places. (00:06:08)
Continuity mistake: When Gambit is saying "Someone may be tracking us," the snaps on both shoulders of his jacket are colored blue, when they should be the same brown color as the rest of his jacket. (00:11:45)
Character mistake: When Rogue asks Storm what her plan is for dealing with the closing walls, Storm says "You three stop the walls, I shall slow the ceiling." Besides Storm and Rogue, Jubilee, Jean Grey, and Gambit are also there, so Storm should have said "You four stop the walls." (00:03:12)
Continuity mistake: When Archangel is lamenting his actions, the communicator devices from Storm's uniform are missing. (00:20:15)
Continuity mistake: When Storm is first watching the World Peace Conference on TV, she is sitting on a couch in a rec room. Moments later, she is watching in a hallway while standing. (00:07:45 - 00:09:00)
Continuity mistake: When Storm is watching TV with her arms folded, her left hand shows her index and middle fingers touching. When the shot changes, it is her middle and ring fingers that are touching. (00:08:40)
Plot hole: After Wolverine tells Gambit that he only knows how to pick pockets and steal candy from babies, Gambit attempts to retaliate by kinetically charging one of the bricks Wolverine is working with in order for it to blow up in his face. Anything Gambit kinetically charges makes a high-pitched humming sound, and Wolverine possesses a superhuman sense of hearing, so he should not have been caught unaware by it. (00:06:55)
Slave Island - S1-E7
Plot hole: When the Leader says "Take me to my car at once!", one of his guards goes to open the door to the room only to have Cable shoot the door with his plasma rifle. The Leader then says "The other way you fool!" and everyone in the room starts running for the windows that Cable shot out a few minutes earlier, which happened to be the only other way out of the room. As evidenced earlier from when Cable shot the windows out, that particular floor appears to be 8 stories up, so if everyone in the room exited through the windows, they would have all fallen to their deaths as all of them were regular humans with no superpowers. (00:17:40)
Slave Island - S1-E7
Factual error: When Professor X is calling Moira McTaggart in Scotland, the phone number he uses is shown to have only dialed the exit code of 011, followed by a fictional seven-digit number with a 555 prefix. Since he is calling from the United States, he would have to dial the country code (44) and area code for the right part of Scotland. Plus UK numbers at that time had at least 9 numbers. (00:08:20)
Plot hole: Towards the end of this episode, Jean Grey nearly falls to her death when a concussion blast from Cable's gun knocks her off a cliff, only for her to be saved at the last moment by Rogue. Apparently Jean Grey and the writers for the episode forgot that her telekinetic powers give her limited flight ability as well as the ability to slow falls, both of which she has demonstrated in other episodes.
Plot hole: Magneto states that he went to Washington, DC to witness Senator Kelly's assassination. But Magneto had no way of knowing about the assassination plot. Mystique was the one who was attempting to assassinate Kelly, and Apocalypse was the one who carried out the order. At this point in the show, Magneto had not worked with either Mystique or Apocalypse, and it's highly doubtful that Mystique would leak the plot, since it was supposed to be covert.
Continuity mistake: The exploding playing card that Gambit uses to destroy a few Sentinels and draw the rest above ground is cleverly shown to be the ace of spades (also known as the death card in some folklore), but the card he is shown charging up before the Sentinels see it is the 2 of diamonds. (00:12:10)
Continuity mistake: When Gyrich is in the car trying to get Trask on the phone, he is shown to be sitting in the backseat on the passenger side (note the windows immediately to his right and behind him). When his driver crashes the car into a tree, Gyrich is shown exiting the car from the front passenger seat. (00:08:00)
Continuity mistake: When Wolverine is searching for Sabretooth and the captive Inuits, his arms suddenly turn yellow. (00:15:50)
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.