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: The clear slime that the alien dribbles is actually KY jelly.
Trivia: The Alien itself has a total of only 4 minutes' screen time in the entire film.
Trivia: There is no dialogue in the first six minutes of the movie.
Trivia: In the chest-bursting scene, the actors had a good idea of what was going to happen, but were unprepared for the amount of stage blood that would be used. According to Ridley Scott, he knew it would be too time consuming to clean the mostly white set and re-shoot the scene, so he captured the creature bursting from Kane's chest in one take. Veronica Cartwright was not expecting to be sprayed directly in the face with stage blood so her reaction is genuine. Tom Skerritt similarly was not expecting such a gory scene and his stunned expression when the creature first emerges is also genuine.
Trivia: When Kane is in the egg pit on the alien ship and shines his light on one of the eggs, the shape we see moving inside is in fact the hands of director Ridley Scott clad in rubber gloves.
Trivia: Originally the design for the alien called for it to have pulsing brains in its head (the idea being so we could see the creature 'thinking' while it moved around). The effects department accomplished this by having live maggots placed underneath the transparent dome on the head. Unfortunately the maggots refused to wriggle and move around on command, so the effects dept. doused them with LSD right before the cameras started rolling. The idea was later scrapped.
Trivia: Originally, director Ridley Scott wanted "Alien" to have a much darker ending. His intention was to have the alien get back on board the shuttle, rip Ripley's head off and then calmly sit down in her chair and record the final transmission, speaking in her voice. The producers understandably found this a little too extreme, so Scott tried changing it to having Ripley go to sleep as normal only for the camera to pull back out of the airlock window and reveal an alien egg, in the process of hatching, attached to the outside of the shuttle (after the "Brett/Dallas egg mutation" scene was deleted, this also had to go).
Trivia: Despite (or maybe because of) their similar style, a bitter rivalry developed between artists H.R. Giger and Roger Dicken. Giger said Dicken's work looked "terrible, like a dinosaur from Disneyland." Dicken in turn called Giger's designs "repulsive abominations." In response, Giger described Dicken as "an awfully aggressive nut" who was "on the verge of a nervous breakdown." The finished film features both artists' designs: Giger's adult xenomorph, and Dicken's facehugger and chestburster.
Trivia: The tendons in the creature's jaws were made using shredded condoms.
Trivia: Writer Dan O'Bannon's idea for Alien evolved from a comedy B movie he'd written a few years earlier called Dark Star which featured an alien that was a beach ball. O'Bannon said that he was unhappy with the silly alien in "Dark Star" and deliberately steered away from potentially comic elements while writing "Alien."
Trivia: When Veronica Cartwright (Lambert) arrived at the studios in England to start working on the film she actually thought that she was to be playing the part of Ripley. It was a mistake by the film makers and quickly rectified. Her agent also thought she was playing Ripley, it's only when the costume designer spoke to her that the mistake was realised.