During a screening, Roger Corman actually smacked an audience member on the head for laughing at the film. When Roger left the theater, the guy he punched poured soda all over his head from the balcony.

Approximately six minutes of footage was removed from the original pre-release assembly on orders of producer Roger Corman, who was angered by witnessing a test screening audience laughing uproariously at some of the comedic passages that were subsequently removed.

The effects footage from the initial space battle is all recycled from Roger Corman's Battle Beyond the Stars (1980).

All releases of the film show the same 77-minute cut, which was released as "Forbidden World", including the theatrical prints. The 2010 DVD release includes the completely uncut version, originally titled "Mutant", on the bonus disc.

Dawn Dunlap's character was originally going to be played by a much older woman, an ex-Playboy Bunny. When Dunlap walked in to audition for the role a day before principal photography was to begin, director Allan Holzman pleaded with the producers to sign her for the part. They very reluctantly made a new contract for her.

This project was originally envisioned as an outer-space version of Lawrence of Arabia (1962) by Allan Holzman. Roger Corman told him that the budget would be far too high, so Holzman eventually decided he wanted to do an Alien (1979) ripoff. Corman agreed to that.

According to director Allan Holzman, just about everything in the movie was recycled from previous productions except for the jumpsuits on the actresses.

There is a creature in one of the crowd scenes in "Star Wars: The Force Awakens" that resembles the Mutant.

Shot in 20 days.

The modular forms decorating the hallways of the research lab are hinged-lid Styrofoam sandwich boxes.

It was director Allan Holzman's idea to not have the robot function that well or have its dialogue clearly understood.

The slaughtered animals in the laboratory were actual dead animals bought from a local pound.

Reuses the same film sets designed by James Cameron for Roger Corman's Galaxy of Terror.

The modular forms decorating the hallways of the research lab are hinged-lid Styrofoam sandwich boxes.

Karen G. Wilson provided the noises for the mutant by cramming a microphone down her throat.

The film was shot in about four weeks with an extra half week devoted to killing the mutant.

Story authors Jim Wynorski and R.J. Robertson based their treatment on Roger Corman's own Attack of the Crab Monsters (1957).

The rather odd choice of music on the cartridge SAM the robot sticks into the spaceship's console during the spaceship battle is the Piano Concerto No. 1 by Ludwig Van Beethoven.

Released on VHS before the BBFC labeling became standard practice.

Susan Justin: The film's composer can be seen on screen as the character of Annie, albeit only in a picture.

During the monster's death scene, it vomits up a viscous pink fluid. This vomit was made up of a material that burns skin on contact. The fearful FX technicians and the second unit director decided to build a wall made of garbage bags to protect themselves, and then stuck a camera through to film the monster's death.

It was producer Roger Corman's idea to kill the mutant with cancer.