Continuity mistake: When Wolverine crashes into the tree knocked over by Sabertooth, notice that the entire front of the truck gets completely folded up and the windshield breaks into a thousand pieces. In the next frame, Wolverine gets thrown through the unbroken windshield and the front of the truck is practically undamaged...
Revealing mistake: Right after the scene where Sabretooth dispatches the Liberty Island guard, the camera switches to a head on shot of Magneto's boat ferrying the torch. As the camera moves upward, you can distinctly see the head of someone crouching down next to Mystique as she captains the boat and it is actually the guard that was the boat pilot.
Continuity mistake: When Mystique reveals herself to Senator Kelly on the helicopter, her blue body is appearing and it shows Senator Kelly watching for a few seconds, but when it shows Mystique again, the blue body thing continues from the part it left off at. It should have been to her legs at the rate it was going at before.
Continuity mistake: At the start when Rogue walks into the bar, when she walks towards the cage, note all the things around her from the camera's perspective (which is from behind her): the wooden plank in front of her which she walks around, and the burning can to the left of the screen. When the camera cuts to the front, the wooden plank is not there and neither is the burning can (now to the right of the screen).
Revealing mistake: In Toad's final scene of the movie, when he is beginning to fight Storm, he leaps into the air onto the balcony railing. If you look at the back of his belt, his wire is very, very obviously visible. There are several times within the movie when Toad or Storm has a wire showing, but none so obvious as that one.
Continuity mistake: When Mystique and Wolverine are fighting, Mystique lifts up a chain link door and Wolverine cuts through it with his claws. It splits and the two pieces go separate ways, yet in the following shot the door is on the floor near Wolverine with only one side cut.
Continuity mistake: Just after Sabertooth has dropped the Senator into the water, the mutated Senator pops out of the water. In the first shot, he is facing the boy, but in the next shot he has his back to the boy, then facing the boy again. Also, when he pops out the water he is only a few feet away from the boy's yellow boat, yet in another shot he is much farther from the boat.
Continuity mistake: When Rogue is seen for the first time, her hand is moving up photographs on the wall, and if you look closely there are some kind of red poppies when she reaches the end, yet when it cuts to another shot a bit further away, her finger is a lot further down the wall from the red poppy/flower.
Continuity mistake: When Cyclops and Storm are in the train station, Storm is held up by Sabretooth, Cyclops spots this and starts to walk over to help. He stretches his arms out between a lot of people to push two people out the way, yet when the shot changes to Toad's POV all the people around him are at least two to three feet away from him.
Continuity mistake: When Wolverine has just walked into Xavier's office for the first time, a girl picks up her book then runs towards Wolverine. Her left hand is on her bag, but in the following shot when Wolverine looks over his shoulder, her left hand is now on the left strap of the bag.
Continuity mistake: When Wolverine and Rogue are in Wolverines truck, just prior to the crash, we see them driving near huge trees with thick leaves that can't be seen through. Yet when Rogue says the line "You really should wear your seatbelt", the view out her window shows a handful of trees that one can through for a mile.
Add timeGavin Jackson
Continuity mistake: When Senator Kelly meets Magneto for the first time, it's outside and cold. When you see Kelly his breath shows blowing to the left of the screen. But when you get the reverse angle of Magneto and Mystique their breath also goes off to the left of the screen. It should be blowing to the right.
Continuity mistake: In the Statue of Liberty, when Toad has shot his slime at Jean Grey's face, we see Cyclops shoot his optic beam to free himself from the room he was trapped in. Then he rushes to Jean's aid. If you look closely you can see that the gloves he was wearing, as part of his costume, are no longer there when he takes the slime off of Jean's face.
Revealing mistake: During the montage that introduces Xavier's School about 27 minutes into the film, you briefly see Cyclops shooting several Frisbees/clay-pigeons out of the air. Watch closely, and you will see that the falling debris from all of the clay-pigeons simply "fades away" shortly after each one explodes. They aren't burning up or disintegrating from his beam. You can see them "fade away" as the animation finishes when each one explodes. A shortcut in the CGI rendering.