Ellen Ripley served as a warrant officer on the ship Nostromo during the ship’s final voyage. When an unknown, alien lifeform attached itself to one of her crew, she attempted to follow quarantine protocol—her efforts were in vain, though, as the ship’s AI MU/TH/UR had other plans. Alone and without hope, Ripley secured the crew's orange tabby cat, Jonesy, and managed to set the self-destruct mechanism on the Nostromo without realizing the alien was one step ahead of her.