The chestbursting scene was filmed in one take with four cameras.
Ridley Scott did all the hand-held camera-work himself.
20th Century Fox doubled the budget from $4.2 million to $8.4 million on the strength of seeing Ridley Scott's storyboards.
Conceptual artist H.R. Giger's designs were changed several times because of their blatant sexuality.
The Xenomorph has 4 minutes of screen time.
During early development, Dan O'Bannon and Ronald Shusett ran into a writing impasse while trying to work out how the alien would get aboard the ship. Shussett came up with the idea "the alien f*cks one of them," which was eventually developed into the facehugger concept. This method of reproduction via implantation was deliberately intended to invoke images of male rape and impregnation, so both writers were adamant that the facehugger victim be a man: firstly because they wanted to avoid the horror cliché of women being depicted as the easy first target; secondly because they felt that making a female the casualty of a symbolic rape felt inappropriate; and thirdly, to make the male viewers feel more uncomfortable with this reversal of genre conventions.
Ridley Scott: [mothers] The Nostromo's computer is named "Mother." The incubation of the alien has also been interpreted as a metaphor for pregnancy.
According to Ridley Scott in the DVD commentary, he had envisioned a moment in the ending scenes of Ripley and the alien in the space shuttle in which the alien would be sexually aroused by Ripley. Scott says that in the scene, after Ripley hides in the closet, the alien would find her and would be staring at her through the glass door. The alien would then start touching itself as if comparing its body to Ripley's. The idea was eventually scrapped.