Alien didn’t use computer graphics, it was acted by a man named Bolaji Badejo who is 6’10″
“As soon as I walked in,” Bolaji told Cinefantastique, “Ridley Scott knew he’d found the right person.” Prior to filming, Badejo was placed on the Nostromo set with a mock-up Alien head and roamed the corridors on film, slithering, pausing, turning, kneeling, and prowling through the corridors to nail an appropriate system of movement for the beast.
“The idea,” says Bolaji, “was that the creature was supposed to be graceful as well as vicious, requiring slow, deliberate movements. But there was some action I had to do pretty quick. I remember having to kick Yaphet Kotto, throw him against the wall, and rush up to him. Veronica Cartwright was really terrified. After I fling Yaphet Kotto back with my tail, I turn to go after her, there’s blood in my mouth, and she was incredible. It wasn’t acting. She was scared.”
This today is one of the bravest and unique Sci Fi-horror films ever made. Remember, no one can hear you scream in space!!!!