Continuity mistake: In the shot of the alien's tail wrapping around the back of Lambert's legs right before it kills her, the floor is different to what it was before, there is water suddenly falling from the ceiling when there wasn't before and her trousers have changed from white to blue. This is because that shot was originally intended to be used when Brett was killed.THGhost
Continuity mistake: In the scene where Joe Gideon is helping his daughter with dance exercises and realises that it is time to put Michelle in a cab, he carries her out of the rehearsal studio with her facing forward and her legs wrapped around his back. They turn a corner to go outside and she magically is facing him arms around his neck and legs wrapped the other way around his waist. Also Michelle suddenly grows a yellow rain jacket. There is no time lapse in the dialog which would explain this turn.
Deliberate mistake: After having wrestled with Santini in his office, Col. Virgil Hedgepath tells Santini, "And no more assaulting corporals in the latrine." Marines use the naval term "head" in refering to the restroom, and would never call it "the latrine." However, since "latrine" is better known to civilians, this could be a deliberate mistake by the film makers.
Continuity mistake: When Apollo Creed is approaching the ring for the rematch at the end of the film, his robe starts off done-up, next shot shows it undone and the towel around his neck loose, and then in the last shot it's back to being neat again with the robe done up. Even when he enters the ring it's all neat and tidy. (01:32:40)