While studying cinema at the University of Southern California, Dan O'Bannon had made a science fiction comedy film with director John Carpenter and concept artist Ron Cobb entitled Dark Star. The film included an alien which had been created using a spray-painted beach ball, and the experience left O'Bannon "really wanting to do an alien that looked real." A few years later he began working on a similar story that would focus more on horror: "I knew I wanted to do a scary movie on a spaceship with a small number of astronauts", he later recalled, "Dark Star as a horror movie instead of a comedy." Ronald Shusett, meanwhile, was working on an early version of what would eventually become Total Recall. Impressed by Dark Star, he contacted O'Bannon and the two agreed to collaborate on their projects, choosing to work on O'Bannon's film first as they believed it would be less costly to produce. O'Bannon had written twenty-nine pages of a script titled Memory comprising what would become the film's opening scenes: a crew of astronauts awaken to find that their voyage has been interrupted because they are receiving a signal from a mysterious planetoid. They investigate and their ship breaks down on the surface. He did not yet, however, have a clear idea as to what the alien antagonist of the story would be.
O'Bannon soon accepted an offer to work on Alejandro Jodorowsky's film adaptation of Dune, a project which took him to Paris for six months. Though the project ultimately fell through, it introduced him to several artists whose works gave him ideas for his science-fiction story including Chris Foss, H. R. Giger, and Jean "Moebius" Giraud. O'Bannon was impressed by Foss's covers for science fiction books, while he found Giger's work "disturbing": "His paintings had a profound effect on me. I had never seen anything that was quite as horrible and at the same time as beautiful as his work. And so I ended up writing a script about a Giger monster." After the Dune project collapsed O'Bannon returned to Los Angeles to live with Shusett and the two revived his Memory script. Shusett suggested that O'Bannon use one of his other film ideas, about gremlins infiltrating a B-17 bomber during World War II, and set it on the spaceship as the second half of the story. The working title of the project was now Star Beast, but O'Bannon disliked this and changed it to Alien after noting the number of times that the word appeared in the script. He and Shusett liked the new title's simplicity and its double meaning as both a noun and adjective. Shusett came up with the idea that one of the crew members could be implanted with an alien embryo that would later burst out of him, feeling that this was an interesting plot device by which the alien creature could get aboard the ship.
Dan [O'Bannon] put his finger on the problem: what has to happen next is the creature has to get on the ship in an interesting way. I have no idea how, but if we could solve that, if it can't be that it just snuck in, then I think the whole movie will come into place. In the middle of the night, I woke up and I said, "Dan I think I have an idea: the alien screws one of them [...] it jumps on his face and plants its seed!" And Dan says, oh my god, we've got it, we've got the whole movie.“ ” —Screenwriter Ron Shusett
In writing the script, O'Bannon drew inspiration from many previous works of science fiction and horror. He later stated that "I didn't steal Alien from anybody. I stole it from everybody!" The Thing from Another World (1951) inspired the idea of professional men being pursued by a deadly alien creature through a claustrophobic environment. Forbidden Planet (1956) gave O'Bannon the idea of a ship being warned not to land, and then the crew being killed one by one by a mysterious creature when they defy the warning. Planet of the Vampires (1965) contains a scene in which the heroes discover a giant alien skeleton; this influenced the Nostromo crew's discovery of the alien creature in the derelict spacecraft. O'Bannon has also noted the influence of "Junkyard" (1953), a short story by Clifford D. Simak in which a crew lands on an asteroid and discovers a chamber full of eggs. He has also cited as influences Strange Relations by Philip José Farmer (1960), which covers alien reproduction, and various EC Comics horror titles carrying stories in which monsters eat their way out of people.
With roughly eighty-five percent of the plot completed, Shusett and O'Bannon presented their initial script to several studios, pitching it as "Jaws in space." They were on the verge of signing a deal with Roger Corman's studio when a friend offered to find them a better deal and passed the script on to Gordon Carroll, David Giler, and Walter Hill, who had formed a production company called Brandywine with ties to 20th Century Fox. O'Bannon and Shusett signed a deal with Brandywine, but Hill and Giler were not satisfied with the script and made numerous rewrites and revisions to it. This caused tension with O'Bannon and Shusett, since Hill and Giler had very little experience with science fiction and according to Shusett: "They weren't good at making it better, or in fact at not making it even worse." O'Bannon believed that they were attempting to justify taking his name off of the script and claiming it as their own. Hill and Giler did add some substantial elements to the story, however, including the android character Ash which O'Bannon felt was an unnecessary subplot, but which Shusett later described as "one of the best things in the movie...That whole idea and scenario was theirs." In total Hill and Giler went through eight different drafts of the script, mostly concentrating on the Ash subplot but also making the dialogue more natural and trimming some sequences set on the alien planetoid.
Despite the multiple rewrites, 20th Century Fox did not express confidence in financing a science-fiction film. However, after the success of Star Wars in 1977 the studio's interest in the genre rose substantially. According to Carroll: "When Star Wars came out and was the extraordinary hit that it was, suddenly science fiction became the hot genre." O'Bannon recalled that "They wanted to follow through on Star Wars, and they wanted to follow through fast, and the only spaceship script they had sitting on their desk was Alien". Alien was greenlit by 20th Century Fox at an initial budget of $4.2 million.
O'Bannon had originally assumed that he would direct Alien, but 20th Century Fox instead asked Hill to direct. Hill declined due to other film commitments as well as not being comfortable with the level of visual effects that would be required. Peter Yates, Jack Clayton, and Robert Aldrich were considered for the task, but O'Bannon, Shusett, and the Brandywine team felt that these directors would not take the film seriously and would instead treat it as a B monster movie. Giler, Hill, and Carroll had been impressed by Ridley Scott's debut feature film The Duellists (1977) and made an offer to him to direct Alien, which Scott quickly accepted. Scott created detailed storyboards for the film in London, which impressed 20th Century Fox enough to double the film's budget from $4.2 million to $8.4 million. His storyboards included designs for the spaceship and space suits, drawing influences from films such as 2001: A Space Odyssey and Star Wars. However, he was keen on emphasizing horror in Alien rather than fantasy, describing the film as "The Texas Chain Saw Massacre of science fiction".
O'Bannon introduced Scott to the artwork of H. R. Giger; both of them felt that his painting Necronom IV was the type of representation they wanted for the film's antagonist and began asking the studio to hire him as a designer. 20th Century Fox initially believed Giger's work was too ghastly for audiences, but the Brandywine team were persistent and eventually won out. According to Gordon Carroll: "The first second that Ridley saw Giger's work, he knew that the biggest single design problem, maybe the biggest problem in the film, had been solved." Scott flew to Zürich to meet Giger and recruited him to work on all aspects of the Alien and its environment including the surface of the planetoid, the derelict spacecraft, and all four forms of the Alien from the egg to the adult.
Casting calls and auditions for Alien were held in both New York and London. With only seven human characters in the story, Scott sought to hire strong actors so he could focus most of his energy on the film's visual style. He employed casting director Mary Selway, who had worked with him on The Duellists, to head the casting in the United Kingdom, while Mary Goldberg handled casting in the United States. In developing the story O'Bannon had focused on writing the Alien first, putting off developing the characters for a later draft. He and Shusett had therefore written all of the roles as generic male ones with a note in the script explicitly stating "The crew is unisex and all parts are interchangeable for men or women." This left Scott, Selway, and Goldberg free to interpret the characters as they liked and to cast accordingly. They wanted the Nostromo 's crew to resemble working astronauts in a realistic environment, a concept summed up as "truckers in space". According to Scott, this concept was inspired partly by Star Wars, which deviated from the pristine future often depicted in science fiction films of the time.
The principal cast members of Alien were:
- Tom Skerritt as Dallas, the Captain of the Nostromo
- Skerritt had been approached early in the film's development but declined as it did not yet have a director and had a very low budget. Later, when Scott was attached as director and the budget had been doubled, Skerritt accepted the role of Dallas.
- Sigourney Weaver as Ripley, the warrant officer aboard the Nostromo
- Weaver, who had Broadway experience but was relatively unknown in film, impressed Scott, Giler, and Hill with her audition. She was the last actor to be cast for the film, and performed most of her screen tests in-studio as the sets were being built. The role of Ripley was Weaver's first leading role in a motion picture, and earned her nominations for a Saturn Award for Best Actress and a BAFTA award for Most Promising Newcomer to Leading Film Role.
- Veronica Cartwright as Lambert, the Nostromo 's navigator/helmsman
- Cartwright had previous experience in horror and science fiction films, having acted as a child in The Birds (1963) and Invasion of the Body Snatchers (1978). She originally read for the role of Ripley, and was not informed that she had instead been cast as Lambert until she arrived in London for wardrobe. She disliked the character's emotional weakness, but nevertheless accepted the role: "They convinced me that I was the audience's fears; I was a reflection of what the audience is feeling." Cartwright won a Saturn Award for Best Supporting Actress for her performance.
- Harry Dean Stanton as Brett, the Engineering Technician
- Stanton's first words to Scott during his audition were "I don't like sci fi or monster movies." Scott was amused and convinced Stanton to take the role after reassuring him that Alien would actually be a thriller more akin to Ten Little Indians.
- John Hurt as Kane, the Executive Officer who becomes the host for the Alien
- Hurt was Scott's first choice for the role but was contracted on a film in South Africa during Alien 's filming dates, so Jon Finch was cast as Kane instead. However, Finch became ill during the first day of shooting and was diagnosed with severe diabetes, which had also exacerbated a case of bronchitis. Hurt was in London by this time, his South African project having fallen through, and he quickly replaced Finch. His performance earned him a nomination for a BAFTA Award for Best Actor in a Supporting Role. He was the only actor aware of the extremely bloody scene of Alien's "birth" in advance.
- Ian Holm as Ash, the ship's Science Officer who is revealed to be an android
- Holm, a character actor who by 1979 had already been in twenty films, was the most experienced actor cast for Alien (he was 46 at the time of filming).
- Yaphet Kotto as Parker, the Chief Engineer
- Kotto, an African American, was chosen partly to add diversity to the cast and give the Nostromo crew an international flavor. Kotto was sent a script off the back of his recent success with Live and Let Die, although it took some time and deliberation between Kotto and his agent before he was offered the part.
- Bolaji Badejo as The Alien
- Nigerian Badejo, while a 26-year-old design student, was discovered in a bar by a member of the casting team, who put him in touch with Ridley Scott. Scott believed that Badejo, at 6 feet 10 inches (208 cm) (7ft. inside the costume) and with a slender frame, could portray the Alien and look as if his arms and legs were too long to be real, creating the illusion that there could not possibly be a human being inside the costume. Stuntmen Eddie Powell and Roy Scammell also portrayed the Alien in some scenes.
To assist the actors in preparing for their roles, Ridley Scott wrote several pages of backstory for each character explaining their histories. He filmed many of their rehearsals in order to capture spontaneity and improvisation, and tensions between some of the cast members, particularly towards the less-experienced Weaver, translated convincingly on film as tension between their respective characters.
Film critic Roger Ebert notes that the actors in Alien were older than was typical in thriller films at the time, which helped make the characters more convincing:
None of them were particularly young. Tom Skerritt, the captain, was 46, Hurt was 39 but looked older, Holm was 48, Harry Dean Stanton was 53, Yaphet Kotto was 42, and only Veronica Cartwright at 30 and Weaver at 29 were in the age range of the usual thriller cast. Many recent action pictures have improbably young actors cast as key roles or sidekicks, but by skewing older, Alien achieves a certain texture without even making a point of it: These are not adventurers but workers, hired by a company to return 20 million tons of ore to Earth.
David McIntee, author of Beautiful Monsters: The Unofficial and Unauthorised Guide to the Alien and Predator Films, asserts that part of the film's effectiveness in frightening viewers "comes from the fact that the audience can all identify with the characters...Everyone aboard the Nostromo is a normal, everyday, working Joe just like the rest of us. They just happen to live and work in the future."
Alien was filmed over fourteen weeks from July 5 to October 21, 1978. Principal photography took place at Shepperton Studios near London, while model and miniature filming was done at Bray Studios in Water Oakley, Berkshire. Production time was short due to the film's low budget and pressure from 20th Century Fox to finish on schedule. A crew of over 200 workmen and technicians constructed the three principal sets: The surface of the alien planetoid and the interiors of the Nostromo and derelict spacecraft. Art Director Les Dilley created 1/24th scale miniatures of the planetoid's surface and derelict spacecraft based on Giger's designs, then made moulds and casts and scaled them up as diagrams for the wood and fiberglass forms of the sets. Tons of sand, plaster, fiberglass, rock, and gravel were shipped into the studio to sculpt a desert landscape for the planetoid's surface, which the actors would walk across wearing space suit costumes. The suits themselves were thick, bulky, and lined with nylon, had no cooling systems and, initially, no venting for their exhaled carbon dioxide to escape. Combined with a heat wave, these conditions nearly caused the actors to pass out and nurses had to be kept on-hand with oxygen tanks. For scenes showing the exterior of the Nostromo, a 58-foot (18 m) landing leg was constructed to give a sense of the ship's size. Ridley Scott still did not think that it looked large enough, so he had his two sons and the son of one of the cameramen stand in for the regular actors, wearing smaller space suits to make the set pieces seem larger. The same technique was used for the scene in which the crew members encounter the dead alien creature in the derelict spacecraft. The children nearly collapsed due to the heat of the suits, and eventually oxygen systems were added to assist the actors in breathing. Four identical cats were used to portray Jones, the Nostromo crew's pet. During filming Sigourney Weaver discovered that she was allergic to the combination of cat hair and the glycerin placed on the actors' skin to make them appear sweaty. By removing the glycerin she was able to continue working with the cats.
Alien originally was to conclude with the destruction of the Nostromo while Ripley escapes in the shuttle Narcissus. However, Ridley Scott conceived of a "fourth act" to the film in which the Alien appears on the shuttle and Ripley is forced to confront it. He pitched the idea to 20th Century Fox and negotiated an increase in the budget to film the scene over several extra days. Scott had wanted the Alien to bite off Ripley's head and then make the final log entry in her voice, but the producers vetoed this idea as they believed that the Alien had to die at the end of the film.
Editing and post-production work on Alien took roughly twenty weeks to complete. Terry Rawlings served as Editor, having previously worked with Scott on editing sound for The Duellists. Scott and Rawlings edited much of the film to have a slow pace to build suspense for the more tense and frightening moments. According to Rawlings: "I think the way we did get it right was by keeping it slow, funny enough, which is completely different from what they do today. And I think the slowness of it made the moments that you wanted people to be sort of scared...then we could go as fast as we liked because you've sucked people into a corner and then attacked them, so to speak. And I think that's how it worked." The first cut of the film was over three hours long; further editing trimmed the final version to just under two hours.
One scene that was cut from the film occurred during Ripley's final escape from the Nostromo: she encounters Dallas and Brett who have been partially cocooned by the Alien. O'Bannon had intended the scene to indicate that Brett was becoming an Alien egg while Dallas was held nearby to be implanted by the resulting facehugger. Production Designer Michael Seymour later suggested that Dallas had "become sort of food for the alien creature", while Ivor Powell suggested that "Dallas is found in the ship as an egg, still alive." Scott remarked that "they're morphing, metamorphosing, they are changing into...being consumed, I guess, by whatever the Alien's organism is...into an egg." The scene was cut partly because it did not look realistic enough and partly because it slowed the pace of the escape sequence. Tom Skerritt remarked that "The picture had to have that pace. Her trying to get the hell out of there, we're all rooting for her to get out of there, and for her to slow up and have a conversation with Dallas was not appropriate." The footage was included amongst other deleted scenes as a special feature on the Laserdisc release of Alien, and a shortened version of it was re-inserted into the 2003 "Director's Cut" which was re-released in theaters and on DVD.
The musical score for Alien was composed by Jerry Goldsmith, conducted by Lionel Newman, and performed by the National Philharmonic Orchestra. Ridley Scott had originally wanted the film to be scored by Isao Tomita, but 20th Century Fox wanted a more familiar composer and Goldsmith was recommended by then-President of Fox Alan Ladd, Jr. Goldsmith wanted to create a sense of romanticism and lyrical mystery in the film's opening scenes, which would build throughout the film to suspense and fear. Scott did not like Goldsmith's original main title piece, however, so Goldsmith rewrote it as "the obvious thing: weird and strange, and which everybody loved." Another source of tension was editor Terry Rawlings' choice to use pieces of Goldsmith's music from previous films, including a piece from Freud: The Secret Passion, and to use an excerpt from Howard Hanson's Symphony No. 2 ("Romantic") for the end credits.
Scott and Rawlings had also become attached to several of the musical cues they had used for the temporary score while editing the film, and re-edited some of Goldsmith's cues and re-scored several sequences to match these cues and even left the temporary score in place in some parts of the finished film. Goldsmith later remarked that "you can see that I was sort of like going at opposite ends of the pole with the filmmakers of the picture." Nevertheless, Scott praised Goldsmith's score as "full of dark beauty" and "seriously threatening, but beautiful." It was nominated for a Golden Globe Award for Best Original Score, a Grammy Award for Best Soundtrack Album, and a BAFTA Award for Best Film Music. The score has been released as a soundtrack album in several versions with different tracks and sequences.