Alien
- Ash
Ash (Ian Holm) is the Nostromo's inscrutable science officer. He administers medical treatment, conducts biological research and is responsible for investigating any alien life forms the crew may encounter. It is at Ash's insistence that the crew investigates the mysterious signal emanating from LV-426. Ripley becomes suspicious of him when he breaks quarantine protocol by allowing Kane, Dallas, and Lambert to re-enter the Nostromo while the Alien facehugger is attached to Kane. Captain Dallas later informs Ripley that Ash had abruptly replaced the ship's previous science officer, whom Dallas had done five previous missions with, just as the Nostromo left Thedus for its return journey to Earth. Over Ripley's objections, Dallas entrusts Ash with all science-related decisions.
After the Alien has killed Kane, Brett and Dallas, Ripley discovers through the ship's computer, "MOTHER", that Ash has been given special orders by the Weyland-Yutani Corporation to ensure the return of the Alien to the company's laboratories, even at the expense of the crew. When confronted by Ripley, Ash attacks her. He is hit in the head by Parker, and the force almost completely severs his head. It is at this point that Ash is revealed to be an android. After suggesting that the crew will not survive the Alien's attacks and giving them his sympathies, Ash is destroyed by Parker using a flamethrower.
- Brett
Brett (Harry Dean Stanton) is an engineering technician on board the Nostromo and a good friend of his engineering chief, Parker. As a 'regular working Joe', he persistently angles for the increased pay and bonus awards he feels are due. He is the first to encounter the fully grown Alien while searching for Jones the cat and the second victim after it injects its inner jaw into his head. He is then dragged into an air duct. In a deleted scene - restored in the 2003 Director's Cut - Ripley and Parker barely see him get carried into the air duct before he is dragged away. His death left Parker clearly distressed. Also in the 2003 Director's Cut, Ripley enters a storage room which the Alien has transformed into its lair. There she finds Dallas and Brett, the first 2 victims of the Alien aboard the Nostromo (and whose bodies had not been found). Dallas begs Ripley to kill him, as he is mutating into an Alien egg. Brett, at a later stage of this metamorphosis, has been almost completely transformed into an Alien egg.
- Dallas
Dallas (Tom Skerritt) is the laid-back captain of the Nostromo; he has sole access to Mother, the on-board computer. Despite his nonchalant and casual-seeming attitude, his leadership and decision-making skills become increasingly evident. He was attacked by the Alien in the air duct tunnels trying to blow the alien out of the ship into outer space through the airlock. In the 2003 Director's Cut, he is later found by Ripley in the Alien's lair, begging to be killed and she complies. Both these scenes give hints that there may have been a closer relationship between them than crew colleagues - an angle further suggested in the Alan Dean Foster novelization (in the book, Ripley asks Lambert if she's ever slept with Ash, hinting at a fair degree of promiscuity among the crew members).
- Kane
Thomas Kane (John Hurt) is the Executive Officer aboard the Nostromo. During the investigation of the derelict space ship, he incautiously moves to get a closer look at one of the unusual 'pod' forms encountered and from this an unknown life-form (later known as an Ovomorph, or face-hugger) attaches itself to his face and (unknown to him and to the crew) impregnates him with an alien creature. Kane remains unconscious while the creature is attached. He regains consciousness after the attached creature dies and falls off. However, the Alien unexpectedly bursts through his chest and kills him during the crew's dinner.
- Lambert
Lambert (Veronica Cartwright), the only other female on the ship besides Ripley, is the navigator of the Nostromo. Disinclined to taking risks beyond the confines of her console, she resents being chosen as one of the team to explore the derelict, and later angry with Ripley for her decision to leave Kane, Dallas and herself outside of the ship when the facehugger was attached to Kane. She expressed a wish to leave the ship when crew members started getting killed off by the Alien. It is during the preparation to leave the Nostromo that, frozen in horror, she witnesses Parker's death, and is killed herself.
- Parker
Parker (Yaphet Kotto) is the chief engineer aboard the ship, with Brett as his assistant. Assertive and acerbic, he is a dauntless complainer and, abetted by his sidekick Brett, demands more money for investigating the alien transmission. Occasionally at odds with Ripley, his respect for her resourcefulness and plans to combat the growing crisis prevails. Devastated by the deaths of Brett and Dallas, he puts all his skills, energies and determination to the task. He and Lambert save Ripley from Ash, and he personally incinerates the nearly decapitated Ash after interrogation. He dies when he is unable to attack the Alien with his flamethrower due to Lambert being in the way. He tries to physically assault the Alien but is almost instantly overpowered. The Alien then impales his head, killing him instantly.
- Ripley
Ellen Ripley (Sigourney Weaver) is the primary protagonist of the Alien franchise, serving as warrant officer aboard the Nostromo. She responds to the growing disasters with characteristic resourcefulness and courage. Her strong distrust of her crewmate Ash after he disobeys her order not to let the infected Kane back on the ship is vindicated when it is revealed that the survival of the crew is not his priority. Ripley (along with Jones the cat, whom she rescued) is the only survivor of the crew's encounter with the alien.
- The Alien
The extraterrestrial species (referred to as "Alien" or "xenomorph") is the primary antagonist of the franchise. The one from Alien (played by Bolaji Badejo) is incubated inside Kane and after being born starts to stalk and prey on the crewmembers of the Nostromo.
Read more about this topic: List Of Alien Characters