Character mistake: When Ripley interfaces with Mother for the first time and sees the special order, an instruction reads as "Insure return of organism" rather than "Ensure return."
Character mistake: When James enters and exits the laboratory, the door has a sign on it that warns for radioactive materials. The laboratory actually contains a biological weapon. Therefore the door should be marked with a bio-hazard symbol. (00:41:00 - 00:42:00)
Character mistake: USA flags are supposed to be displayed with the Union (blue area) on top left corner, whether it's displayed horizontally or vertically. USA missiles at times displayed the flag backwards. Also, at the end of the movie, the flag hung on the hangar next to the USSR flag is backward. (01:40:57)