In *Alien*, the android aboard the Nostromo is Ash.
Ash serves publicly as the ship’s science officer, handling biological research and helping investigate the mysterious transmission from LV-426. His apparent loyalty to the crew hides a secret corporate directive from Weyland-Yutani.
After Kane is attacked by a facehugger, Ash violates quarantine rules and allows Kane back aboard. Later, Ripley discovers that Ash has been ordered to preserve the alien organism, even if the entire crew dies. When confronted, Ash attacks Ripley, revealing his artificial nature.
Ash is often confused with Bishop, another android played by Ian Holm’s fellow franchise performer Lance Henriksen. Bishop appears in *Aliens*, not the original *Alien*. The name Rook belongs to a later synthetic character in *Alien: Romulus*, while David is associated with the *Prometheus* films.