In Alien, the science officer whose android identity is revealed is Ash.
Ash serves aboard the commercial spacecraft Nostromo and initially appears to be a human member of the crew. Later, after sustaining severe damage, he is exposed as a synthetic person. The discovery changes the crew’s understanding of the company’s priorities and of their mission orders.
Ian Holm played Ash in Ridley Scott’s 1979 science-fiction horror film. The character’s synthetic nature is deliberately concealed from the crew, making the revelation one of the film’s major turns.
Ash is often confused with Bishop, the android played by Lance Henriksen in Aliens. Bishop is a different character in a later film and is portrayed as more openly cooperative. Alien’s android storyline also introduces the recurring theme of corporate interests treating human crews as expendable.