I’m surprised that no one has mentioned that Alien is clearly an unattributed remake of the 50’s film “It, The Terror From Beyond Space.”
And that film was written by Jerome Bixby who wrote the 1953 story “It’s a Good Life” which was the basis for a 1961 episode of The Twilight Zone and which was included in Twilight Zone: The Movie (1983). He also wrote four Star Trek episodes: “Mirror, Mirror”, “Day of the Dove”, “Requiem for Methuselah”, and “By Any Other Name”. With Otto Klement, he co-wrote the story upon which the classic sci-fi movie Fantastic Voyage (1966), television series, and novel by Isaac Asimov were based.