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.
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's 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: 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.
Question: Question about the Director's Cut of the film. The scene where Brett is looking for Jones has been altered slightly - when he looks up at where the water is dripping from, you can actually see the Alien hanging motionlessly from one of the chains. Has Ridley Scott given an explanation as to why he added this new dynamic to the scene? It's easy enough to speculate why, but a link to an 'official' explanation would be appreciated.