The line "I have come here to chew bubble gum and kick ass, and I'm all out of bubble gum" was ad-libbed by Roddy Piper. According to director John Carpenter, Piper had taken the line from a list of ideas he had for his pro wrestling interviews.
The big fight sequence was designed, rehearsed and choreographed in the back-yard of director John Carpenter's production office. The fight between Nada (Roddy Piper) and Frank (Keith David) was only supposed to last twenty seconds, but Piper and David decided to fight it out for real, only faking the hits to the face and groin. They rehearsed the fight for three weeks. Carpenter was so impressed he kept the five minutes and twenty seconds scene intact.
Roddy Piper's character never gives his name nor is he referred to by name throughout the entire movie. He is simply referred to as "Nada" in the credits, which means "nothing" in Spanish. The name is most likely a reference to George Nada, the main character of Ray Nelson's short story "Eight O'Clock in the Morning," which was the basis for 'They Live'.
According to a title-card in the made-for-DVD short documentary He Lives: Interview with John Carpenter (2013), "They Live opened at the #1 at the US box office. And disappeared from theaters soon afterwards".
For years after the film's release - and even on the movie's DVD commentary - Roddy Piper maintained that the film was based on an actual incident in the 1950s in which a company manufactured a TV that planted subliminal messages in women's brains instructing them to make extravagant purchases. Piper was unaware that the "documentary" he had seen, L'affaire Bronswik, was in fact a comedy short produced in 1978.
The film was made and released about twenty-five years after its source short story "Eight O'Clock in the Morning" by Ray Nelson had been first published in 1963. According to John Carpenter, this movie was also based on an Eclipse Comics comic-book adaptation of this story.
Many movie posters for the film featured a long blurb that read: "You see them on the street. You watch them on TV. You might even vote for one this fall. You think they're people just like you. You're wrong. Dead wrong.".
One of two major Hollywood studio science-fiction films released in the year of 1988 that featured alien characters assimilated into modern day society on the planet Earth. The films are Alien Nation (1988) and John Carpenter's They Live (1988).
The film is partially shot in black-and-white which involved only the scenes and sequences where the aliens were visible to the audience when characters are wearing the sunglasses for most of the film. But this visual aesthetic ceases towards the end of the picture whereupon the aliens become visible in color for the film's final act.
In a certain point in the movie, the main character says, when facing the aliens for the first time (due to the dizziness caused by the glasses, he isn't aware they're aliens) that "You need a Brazilian plastic surgeon". That's probably a nod to then internationally famous Brazilian plastic surgeon Ivo Pitanguy.
The aliens superficially resemble walking, rotting corpses. Carpenter didn't want the aliens to look like the "high-tech" creatures of other science fiction films. He decided that since these beings were corrupting humanity, they themselves should resemble corruptions of human beings.
After finishing They Live, John Carpenter was gonna direct an action horror film Shadow Company sometime around 1989. Written by Shane Black and Fred Dekker, movie was gonna be produced by Walter Hill (who also co-wrote some of the script) and with Kurt Russell in main role. The script was about group of US special forces soldiers who died during Vietnam war and years later after their bodies are brought back the soldiers, who were members of army project which involved some dark experiments, rise up from the graves soon after they were buried and proceed on raiding the armory from nearby army base and attack the town in which they were buried, killing everyone in it and wiping it off the ground during Christmas night. Due to some problems in pre-production, the movie was never made, although original script has gained cult following from fans of Carpenter, Black and Dekker.