Revealing mistake: Despite Sigourney Weaver supposedly having had her fingers cut off if you watch her when she's in her straitjacket you can see her fingers moving around.
Continuity mistake: Mikey dropped the wristwatch Andrew gave him and it landed face down with the bands upward. When Mikey jumped off the rock to retrieve it, the watch's face was on its side (visible to the screen) and the bands were parallel to the ground. (00:05:04)