Ellen Ripley: Once fully grown, the Xenomorph picks off the crew of the salvage ship Nostromo one by one, until only Warrant Officer Ellen Ripley (and the ship's cat, Jones) are left to deal with the creature.
Screaming Xenomorph: While investigating a derelict spaceship, a member of a salvage crew is attacked by an alien parasite. It implants and embryonic life-form which grows and escapes, becoming the horrific Xenomorph.