*Between Aliens (1986) and this movie, the style of hyper-pod on the Sulaco and the color of the lettering on the Sulaco’s hull changed.
*- The bloodstain on the Clemons’ overalls changes size twice when the governor arrives during the autopsy.
*- Facehuggers are able to lay only one embryo then die. The facehugger that impregnates Ripley shouldn’t have been able to impregnate the dog as well.
*- Dillon’s glasses disappear for a shot after he asks Ripley “What? What do you think?”
*- When 85 and Ellen Ripley are at the scanner, he says that he is not able to operate it, however in a later shot he does.
*- Prisoner Golic is never killed and is not shown to be present when Morse and the “rescue team” leave the planet at the end of the film. The last we see of him is when the doctor is killed by the alien. (A sequence in the pre-release version showed him getting killed after freeing the alien from the vault.)