The 1979 film Alien introduced us to one of the more terrifying visions of extraterrestrial life, a ten-foot tall parasite that will keep you alive just long enough to aid in its reproduction. It also introduced us to badass character Ellen Ripley, played by Sigourney Weaver. We weren’t used to women action heroes in 1979.
5. RIPLEY WASN’T SUPPOSED TO BE A WOMAN.
[Screenwriter Dan] O’Bannon and [writer Ronald] Shusett wrote the entire cast as men, but they left a note in the screenplay that “the crew is unisex and all parts are interchangeable for men or women.” Shusett admits they never dreamed of the lead being a woman, though. The producers made that call, believing a female Ripley would be more unique but also more palatable to their bankrollers. As Brandywine producer David Giler remembered, “Looking it over, [producer Walter Hill] and I thought, ‘Here’s this one character who’s not too interesting.’ And this studio—I hate to say this, but for very cynical reasons—this studio [20th Century Fox] is making Julia and Turning Point and they really believe in the return of the woman’s movie. [We’d] probably get a lot of points if we turn this character into a woman.”
11. ROGER DALTREY HELPED WITH THE LIGHTING.
When the Nostromo crew disturbs the facehuggers, there's a beam of blue light, which indicates early trouble. And you have The Who to thank for that. Lead singer Roger Daltrey was experimenting with lasers right next to the studio where Alien was shooting, and he graciously lent his equipment out to Scott.
Read the rest of the trivia from the production of Alien at mental_floss.