X-Men 2 (2003)

Continuity mistake: When Wolverine attacks the SWAT member in the Mutant Academy kitchen while Iceman takes cover, there's a spot the difference competition between the start and end of the gunfight. After a second or two there are bullet holes in the back wall, the Dr. Pepper's been knocked over, the basket's gone from the corner of the table, and the chair at the right is maybe a foot from the corner. When we cut back, the bullet holes in the wall have changed position, the Dr. Pepper's righted itself, the basket's back on the corner, and the chair's now much closer to the edge. All this while Iceman's hiding and Wolverine and the gunman are fighting each other. (00:36:40)

Policeman: Put the knives down!
Wolverine: I can't.

Trivia: Magneto is reading 'The Once and Future King' by T H White. In the novel Merlin is trapped in a crystal cave - Magneto in a similar plastic/glass cave.

Question: Why does Charles look out of the window in the end of the movie, when he's teaching a class?