Other mistake: When Professor X says "We must do all we can to defeat the Phoenix within her," there is a black spot that moves vertically across the screen as the camera is panning from Cyclops to Wolverine. It's as if there was a small bug on the lens.
Other mistake: When Apocalypse is holding Rogue upside-down, her belt remains in place despite the fact that her belt is wider than her waist and abdomen (it is not as wide as her hips which is why it remains in place when she is upright). Her belt should have fallen down to underneath her breasts.
Other mistake: During the "Previously on X-Men..." segment before the show's intro, it shows the Juggernaut landing in the ocean and walking across the ocean floor after Gladiator had hurled him away. However, Juggernaut's fate was never actually shown after Gladiator threw him. He was only seen fading off into the distance.
Other mistake: When Corsair is running towards the Starjammers and Storm at the top of the Mayan structure, Lilandra can be seen among the group despite the fact that she was not in the episode before or after this moment. This was most likely supposed to instead be Jandra, the Shi'ar child that the Starjammers were trying to protect.
Other mistake: When the X-Men and Corsair encounter D'Ken in the hallway, D'Ken, Gladiator and Lilandra remain in the background while the X-Men and Corsair are wiped from the screen. It's as if this was meant to be a zoom in on D'Ken, Gladiator and Lilandra, but their size relative to the camera remained the same and the X-Men and Corsair are simply removed from view.