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.
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.
The trivia items below may give away important plot points.
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.