Continuity mistake: After Rogue absorbs Blob's powers to stop him from collapsing the bleachers, the shot changes, and we see Blob falling to his knees, and Rogue standing directly behind him. The shot changes again, and Rogue is suddenly crouched down on the rubble with Kitty standing behind her, and Blob nowhere to be seen.
Continuity mistake: When Principal Kelly is placing the caution tape across the destroyed restroom wall, he applies it at a diagonal angle. When the shot changes, the tape is now at a horizontal angle, and he is now applying a second piece at a diagonal angle.
Factual error: After Alex is dragged underwater by the harness tether, Scott goes swimming after him and easily locates him. Given that they are in the middle of the ocean at nighttime during a heavy rainstorm, and Scott is wearing sunglasses, it would be way too dark below the surface to see anything.
Factual error: The map of the western United States shown during the weather report at the start of the episode shows some states drawn incorrectly. Idaho's entire western border is a straight line, whereas in real life, Oregon has a horn-shaped indentation on its northeastern border that it shares with Idaho. Idaho also looks like a crude staircase, with the southwestern border of Montana going down to central Wyoming, whereas that area in real life is around the northwestern part of Wyoming.
Audio problem: In the scene where Mystique returns to the Brotherhood house, when Pietro says that their team is as tough as ever, it's Lance's voice that comes out of his mouth.
Revealing mistake: When Wanda traps Magneto in the force field thing, for one shot, Magneto is missing a sleeve on one arm, then it comes back a shot later.