Warrant Officer Ripley
Ripley is the strong-willed, practical protagonist of Alien. The Warrant Officer, Ripley assumes authority over the shuttle when her superiors leave the Nostromo to investigate the source of the alleged distress signal. She has a keen sense of what is best and a solid authority, but her judgment is often overlooked and undermined by her male crew mates. She fights back against these injustices, and proves to be the savviest member of the crew by far.
Ripley's story is one of survival, as she is left the only crew member standing on a ship threatened by the terrifying alien lurking on board. Not only must she contend with the alien, but also with the corrupt corporate interests of those who commissioned the Nostromo, who would have the alien delivered to Earth at the expense of her life. Ripley is principled, brave, tough, and crafty in her journey to survive.
Captain Dallas
Dallas is the Captain of the Nostromo, and takes his job seriously. However, he is prone to lapses in judgment as well, as when he lets Kane aboard without going through proper quarantine procedure. Dallas' demise comes when he seeks to trap the Alien in an airlock. He is quickly ambushed by the creature in the narrow labyrinth of the air ventilation shafts, making for one of the most effective jump scares in modern cinema. He is a gruff man who wants to do what is best, but is less discerning than his inferior, Ripley. When Ripley tells Dallas she doesn't trust Ash, he can only manage to say, "I don't trust anybody."
Science Officer Ash
Ash is the Science Officer on the Nostromo, and as such takes the scientific approach to the question of the dark and mysterious alien. He seeks to learn about the alien life form, despite the death and damage that the creature might create. By overriding Ripley's quarantine when Kane is initially attacked, and then again preventing Ripley from killing the alien, Ash proves himself to be a cold-hearted and remorseless character. These traits are made all the clearer when Lambert, Parker, and Ripley discover he is an android, programmed to complete tasks regardless of their human consequences.
Ash's story is resonant with the character of the monster in Mary Shelley's Frankenstein, who is also willing to perform morally condemnable actions in the name of science. Ash represents the moral failure of science, and its corruptibility.
Warrant Officer Kane
Kane is an officer on the Nostromo whose curiosity leads him to volunteer to follow the unknown transmission and explore the alien spacecraft. After discovering a strange room full of eggs, Kane is attacked by a small alien that implants an egg in his body. While we do not learn much about Kane, he is the crew member who suffers the most violent and grotesque fate in the film, as his body essentially becomes an egg from which the alien hatches, killing him.
Chief Engineer Parker
Parker is the chief engineer aboard the Nostromo, who handles the repairs to the ship. He adamantly opposes going to investigate the distress signal from LV-426, due to a lack of crew training. He also worries about getting a fair salary that reflects the extension of the mission. Parker is comical and good-spirited in the beginning, cracking jokes and boosting crew morale, but once the alien is loosed on the ship, he becomes frightened and aggressive, aiming to kill it at whatever cost. He is a heroic character, saving Ripley from the aggressive android Ash. Parker dies when the alien corners him and Lambert while they gather supplies for an escape.
Engineering Technician Brett
Brett is a quiet and compliant engineering technician who works under Parker. Once the alien is loose, Brett makes several cattle prods and nets to capture it, with motion detectors to track it. Brett is also the first to be killed by the adult alien, while searching for the cat Jones aboard the ship.
The Alien
The alien, as it is referred to, or xenomorph, as it is officially called within the franchise, is the driving antagonistic force in the film. It is roughly humanoid, with four limbs and a head atop its shoulders, but also has a devil-like tail and lacks facial features other than long jaws. Its outer jaws open to reveal a smaller mouth, which shoots out to break the skulls of its victims. The alien has no eyes, cannot speak or communicate with humans in any way, and appears to only act out of an instinct to kill. The xenomorph represents the fear of the unknown, the things outside human control, and death.
Jones
A cat
