Depending on whom you ask, Alien is either pure science fiction or cold-blooded horror masked in extraterrestrial dressings. Whichever side one falls on, though, there’s no denying the fact that Ridley Scott’s film is as visceral and horrific as genre flicks come, and that’s exactly how he intended it to play.

Before heading into production, screenwriter Dan O’Bannon advised Scott to watch director Tobe Hooper’s infamous The Texas Chainsaw Massacre, as a way to see firsthand what the day’s ballsiest filmmakers were doing; prior to Alien, the England-born Scott had no horror experience, with only the award-winning historical drama The Duellists (1977) to his credit.

As the story goes, Scott sat down to watch Chainsaw inside the 20th Century Fox screening room; with the film playing in all of its grotesque glory, Alien co-writer Walter Hill, with a Coke and a hamburger in hand, stopped in to see Scott, viewed the movie alongside him, and never touched his burger or drink the entire time.

That full soda and cold patty convinced Scott that the Chainsaw model was the way to go. The result: Alien’s unforgettable “chestburster” sequence, one of cinema’s all-time great shocks.