Jason X (2001)

Revealing mistake: When Kay-Em kicks Jason in the face during the fight sequence, you can see Kane Hodder's goatee. (01:03:40)

Revealing mistake: When all of Rowan's clothes are removed from her frozen body, the outline of a strapless bra can be seen under the metal blanket. It is also seen later when she sits up and the metal blanket slips a little bit. (00:21:15)

Revealing mistake: After Jason gets his arm blown off, you can see that his torso is much bigger than before since the actor had to hide his arm somewhere. (01:05:10)

Revealing mistake: When Uber-Jason punches off Kay-Em's head, you can see that it is already rolling off her shoulders before he hits her. (01:11:10)

Revealing mistake: When Sgt. Brodski gets a spear through him, Jason pushes it through the wall and passes into Brodski's stomach. You see him lift himself up off of the wall and the spear in his stomach lifts up as well. (00:47:40)