Hicks was originally played by James Remar, but Michael Biehn replaced him a few days after principal photography began, due to "artistic differences" between Remar and director James Cameron.
The preparation for the actors playing Colonial Marines included two weeks' training with the S.A.S. (Special Air Service, Britain's elite anti-terrorist force) and reading Robert Heinlein's novel "Starship Troopers (1997)". Michael Biehn missed the training, as he was a last-minute replacement.
The mechanism used to make the face-huggers thrash about in the stasis tubes in the science lab came from one of the "flying piranhas" in one of James Cameron's earlier movies Piranha Ii. It took nine people to make the face-hugger work; one person for each leg and one for the tail.
The APC was modeled after an airplane tug.
Only six alien suits were used. The appearance of hundreds of aliens is simply clever editing and planning.
The body mounts for Vasquez's and Drake's smart guns are taken from Steadicam gear.
The pulse rifles that the Marines use are made from a Thompson M1A1 machine gun with a Franchi SPAS 12 shotgun underneath.
The M-56 smart guns and the sentry guns built for the movie were designed around German MG 42 machine guns.
The helmets the Marines wear are modified M-1 ballistic helmets.
There were two versions of the "Bug Stompers" logo designed for the movie, one wearing sneakers, and one wearing combat boots as seen on the drop ship.
A lightweight dummy model of Newt (Carrie Henn) was constructed for Sigourney Weaver to carry around during the scenes just before the Queen chase.
The armor for the film was built by English armorer Terry English, and painted using Humbrol paints.
The camo pattern worn by the marines is actually called "frog and leaf" and its use and production has been discontinued.
None of the models or the original designs of the Sulaco from Alien (1979) could be found, so set designers and model-makers had to reconstruct the model of the ship and the interior set from watching Alien (1979)).
Bishop's Knife trick was previously in Roman Polanski's Knife in Water (1962)
"Sulaco" is the name of the town in Joseph Conrad's "Nostromo". See also Alien (1979).
Michael Biehn's character gets bitten on the hand by another character. This happens to him in every James Cameron movie he's in - see The Abyss (1989) and The Terminator (1984).
The music heard at the beginning of the movie while the ship is drifting in space is from the Gayane Ballet Suite by Khachaturian. This music is also featured in a shot of a ship hovering above the moon in Stanley Kubrick's 2001: A Space Odyssey (1968).
"She thought they said 'illegal aliens' and signed up..." said Hudson. This line (directed towards Vasquez) was in inside joke amongst the actors. Jenette Goldstein (Vasquez) had gone to the audition thinking the film would be about illegal immigrants. She arrived with waist-long hair and lots of makeup. Everyone else was wearing military fatigues.
One of the sets was kept intact after filming. It was later used as the Axis Chemicals set for Batman (1989).
The "special edition" includes extra scenes: Newt's parents discovering abandoned alien ship on LV-426, scenes of Ripley discussing her daughter, Hudson bragging about his weaponry, robot sentry guns repelling first alien raid, Hicks and Ripley exchanging first names. Also included is a scene on LV-426 where a child rides a low-slung tricycle similar to one ridden in The Terminator (1984), also directed by James Cameron.
During the scene inside the APV preparing for battle, "El riesgo vive siempre!" can be seen scrawled in white across Vasquez's armor. This is Spanish for "The risky always live!"
Composer James Horner cannibalized some of his scores from Star Trek II (1982) and Star Trek III (1984).
Al Latthews, who plays a Marine sergeant in this film, was in real life the first black Marine to be promoted to the rank of sergeant in the field during service in Vietnam.
A scene on the colony before the alien infestation was deleted from the final cut. Elements of that scene show up in later James Cameron projects.
The line, "...and we always get the same answer: 'Don't ask'" was used in Terminator 2 (1991)).
The character name "Lydecker" was used in James Cameron's "Dark Angel".
All the marines (with the exception of Hicks) use their real life first names as their characters' first names.
In both the standard and special addition VHS versions, the fifteen-minute countdown at the end of the film is indeed fifteen minutes.
The set for the main corridor of the colony was the set used for the corridor in the Vogon spaceship in "The Hitchhiker's Guide to the Galaxy" (1981) misi-series.
Ripley's (Sigourney Weaver) daughter was played by Weaver's mother.
As the final credits fade, there is the sound of an alien egg opening.
The Special Edition restores 17 minutes of footage cut from theatrical version. The new scenes:
The laserdisc edition also includes the sound of a face-hugger scurrying from left to right as the final credits fade.
- Ripley is sitting on a park bench waiting for Burke (before the inquisition), immediately following her stay in Gateway Station' hospital. She presses a button, and the entire park behind her disappears, revealing a gray screen. Burke enters and tells her how to act at the hearing. Ripley asks about her daughter. Burke keeps talking about the hearing. She insists to hear about her daughter. Burke hands her a computer printout (color) that shows her a nice old lady. Burke tells her that her daughter died at the age of 67. That was two years ago. Ripley whispers that she promised her daughter she'd be back before her 11th birthday before going off on the Nostromo.
- After Ripley's outburst during in the inquest ("Because if one of those creatures gets down here, you can kiss all of this goodbye"), dialogue has been restored in which Van Leuwen voices the council's final decision. (Her flight status is revoked because she is deemed unfit to serve as a flight officer, she has to have monthly psych evaluations, and no criminal charges being filed against her)
- A scene where the colonists receive orders from Burke telling them to explore the derelict spacecraft. Newt's family drives to the site, during the trip Newt and her brother Timothy are arguing about a game of hide and seek that they play in the colony's air duct system. Timothy complains that Newt has the unfair advantage of being able to hide in the small places that the rest of the players can't get to. Following this, they arrive at the derelict ship and the mother and father go in; later the mother returns dragging the father who now has a face hugger clamped on his face.
- There's a scene of the colony, before contact with the aliens, in this scene we see a sign outside the colony reading: "Hadleys Hope - pop. 158"
- During the sequence in Ripley's apartment (where they try to convince her to go investigate the lack of contact with the Colony), Burke's dialogue regarding "The Company's" interest in the colony has been restored.
- Immediately following the establishing shot of the Sulaco is a restored introduction to the interior of the ship, eventually leading to the frost-covered hypersleep chamber (and then they wake-up. this is similar to the start of Alien).
- During the drop from the Sulaco to LV-426, is a restored scene of Hudson playfully boasting about the Marines and their weaponry. He tells Ripley he'll protect her. He also tells her the Sulaco carries every weapon from knives to 'nukes'.
- During the Marines' initial search through the colony, a sequence has been inserted in which Hudson investigate some motion they have detected ahead of them. It was some mice walking around in their cage.
- The scene in which Ripley, Burke, Gorman, and Bishop enter the colony has been restored. (You see lots of hesitation on Ripley's face before entering the complex). Hicks leaves behind, asks her if she's ok. She says yes and enters the complex.
- During Hick's discussion of the equipment salvaged from the APC wreckage, additional dialogue has been added in which he describes the four remote sentry guns and how they can be used.
- When Ripley and the Marines examine the colony's blueprints, discussing how they will barricade themselves inside the complex, there is some additional dialogue referring to the strategic placement of the sentry guns.
- The sequence of Hicks arming the sentry, and Hudson and Vasquez testing one of the sentry guns has been restored.
- Before the scene where Ripley carries Newt into the infirmary, a single show of the sentry guns has been inserted.
- During the scene where Ripley puts Newt to bed in the medical center, the dialogue about Ripley's daughter and the origin of babies as been restored. Newt asks Ripley if human babies are born the same way the aliens are. (Newt asks if Ripley ever had a daughter and she finds out Ripley's daughter's dead).
- In the scene where Ripley, Bishop, Hudson, and Vasquez discuss the aliens' life cycle, there is some additional dialogue in which Hudson, Vasquez and Bishop offer their speculations. (Beehive/anthill sort of society)
- After Ripley's confrontation with Burke, the sequence involving the aliens attempting to make their way past the sentry guns in the service tunnel has been restored.
- Something probably only showed at the opening day of Aliens was a scene in which Ripley puts on her Reebok sneakers after she just found out that the facehuggers broke free, when she rested with Newt in the MedLab.
- After Vasquez and Ripley seal Bishop in the pipe, the aliens confront the other two sentry guns that have been set up in the colony corridors. At the end of the sequence, when Hicks dispatches Hudson and Vasquez (to walk perimeter), some of the shots have been rearranged from the theatrical edition and Hicks' dialogue slightly altered.
- Before Ripley leaves the drop-ship to rescue Newt, there is some additional dialogue in which she turns to Hicks to say goodbye, and they exchange their first names (Ellen Ripley and Dwayne Hicks).
- An additional scene shows Ripley searching for Newt and finding Burke who has been cocooned and impregnated. Burke begs Ripley to shoot him, instead she hands him a grenade. This scene does not appear in any released version but was filmed (some magazines printed a few shots taken from it).