According to Brett Piper, a distributor said that if he wanted his movies to succeed overseas, they should have all action and no dialogue. Piper made this movie and showed it to the same distributor, who said "Geez, I can't sell this thing, there's no dialogue!"
Brett Piper be wrote a sequel Nymphoid II: Return to Dinosaur Hell and pitched it to Lloyd Kaufman at Troma. He seemed enthusiastic but it turned out he wanted Piper to raise the money himself, produce the film, and hand the finished product over to him, in return for which Piper would receive essentially nothing. So Piper passed.
Brett Piper said in a 2012 interview that the idea for the movie started when one of the actors he worked with in Mutant War (1988) asked if Piper would produce a film with him if he could raise the money. Piper agreed and they started batting around ideas. They finally settled on an old script Piper had written called Dark Sun, which they later changed to The Dark Fortress (later retitled again by Troma). Piper said he wanted to see if he could make a Ray Harryhausen-style period film with castles and monsters and costumes and such, but with very little money, and, of course, naked women. He thinks they succeeded, though the film doesn't hold up that well today, and they should have had more naked women.
The character Clon was named after Mike Mazurki's character in the classic sitcom It's About Time (1966), according to Brett Piper.
Lead actors Paul Guzzi and Linda Corwin's only role.