Trivia: When James Brolin was offered the role of George Lutz, he was informed that they didn't have a script to give him. James bought a copy of the novel and began to read it. At two o'clock in the morning, while reading a very intense part of the book, a pair of pants that he had hung up earlier fell to the ground causing him to jump in fright. After that, James agreed to do the film.
Trivia: Ripley abruptly yelling at Parker to "Shut up!" is not in the script. Fans and industry gossip have long speculated that this was Sigourney Weaver breaking character in frustration and she was in fact telling Yaphet Kotto to "shut up" so she can finish her lines. The sequels 'Aliens' and 'Alien 3' both feature scenes where one of the normally cooler-headed protagonists suddenly snaps at a ranting character to "shut up!" in apparent reference to this moment. (01:16:50)
Trivia: All rats used in this movie where imported from Hungary and were originally white. Only black rats can pass the plague, so all rats where painted black or grey right before the film shots. (01:33:35)
Trivia: The scenes where the child vampires float around outside or float into the bedrooms of their victims were partly filmed in reverse to make them seem more "unnatural."