Continuity mistake: In the scene in the apartment, where the Terminator cuts the flesh away from his damaged eye, he picks up a hobby knife that has a blade attached. In the next shot, as he lifts the knife up toward his eye, the blade has disappeared. Then in the front-on shot the blade is back again. (00:52:35)
Revealing mistake: When Nancy is running up the stairs in her house to escape Freddy for the first time her foot hits the steps and go through the steps into some goop. Look at the steps above that step and you can see the pre-cut holes where the next sets of goop will be. (00:39:10)
Continuity mistake: When doctors are discussing the medical condition of Dave Bowman's mother, a close-up of the African-American doctor shows a framed newspaper on the wall behind him. It is the front page and has prominent pictures of Bowman and Poole taken during their mission. In the next, wider shot, we see this wall suddenly has nothing on it - the newspaper and frame have vanished. They return when Bowman's mother sits up in bed. (01:16:45)
Continuity mistake: In the scene early in the movie where Kirk is talking to Sarek the guns on the wall are suddenly rearranged. (00:23:50 - 00:24:45)
Continuity mistake: During the first chase scene, the semi passes by an empty taxi cab and when the camera angle changes, the semi crashes into the same taxi cab. (00:06:05)
Revealing mistake: At the climax of the exorcism scene, Christie begins spinning at great speed. That's an impressive supernatural feat already, but the real scary part is that to do, so she also transmorphs into a dummy. (00:52:40)