Unit director James Cameron got maggots to wriggle on a severed arm by passing an electric current through it, impressing a couple of producers and earning him his next job, and so, his film career was born.
Originally, Taaffe O'Connell's character was supposed to be attacked and eaten by the giant worm. The change to her being raped by it was a last minute decision by director Bruce D. Clark. While she didn't object to doing nudity, she was upset by the fact that the set and the slime that she had to be coated with were both freezing the day of the shoot.
Sid Haig didn't think the dialogue in the script matched the character of Quuhod, so he asked Roger Corman if he could play Quuhod as a near mute instead. Corman agreed and let Haig portray Quuhod with almost no dialogue. Haig only says a single line in the whole movie.
The film went into production in the spring of 1981 at the Hammond Lumber Co. lot in Venice, CA, where New World's studio facilities were located. Additional sets, including the surface of the planet and the exterior of the pyramid, were built at a soon-to-be demolished Bekins Storage facility.
The trivia item below may give away important plot points.
The movie was originally rated X by the MPAA. The following cuts were made for an R rating: scenes of evisceration and a protracted shot of a scalped corpse with part of its skull missing, several frames from the infamous worm rape scene showing giant worm's thrusting movements and victim's face in ecstasy, sounds of bones breaking from a scene in which another female character gets crushed by living wires. Original X-rated version of the movie is confirmed to be lost and destroyed.