American actor Bruce Glover plays two uncredited roles in this film, a "Martian Crewmember" and Mull the Space Monster, but Glover is best known for being the father of "Back to the Future" star Crispin Glover, and playing the assassin Mr. Wint in the James Bond film "Diamonds Are Forever".
At approximately 49:00 into the film, several of the Martians are seen carrying hand-held weapons that are actually modified Wham-O Air Blasters, a popular toy in the 1960s.
Written by Virginia-based university writers R.H.W. Dillard, George Garrett and John Rodenbeck, this film was originally conceived as a comedy and a parody of the science fiction and horror genres, but the producers, while they were amused, wanted a serious science fiction/horror film instead. Comedic elements from the film's script that were cut from it included Col. Frank Saunders/Frankenstein being partially made from transplanted human parts, including the legs of a dead tap dancer (and, as a result, whenever he heard the song "Sweet Georgia Brown" he would immediately start to tap dance and not stop, no matter what the situation was).
Just as filming was completed, director Robert Gaffney felt that the film needed more action, so he filmed additional scenes of Col. Frank Saunders/Frankenstein fighting Mull the Space Monster aboard the Martian spaceship in its ending. Gaffney and crew member Joe King (who also had a bit role in the film as "Lieutenant Denny") stood in for both Robert Reilly (Saunders/Frankenstein) and Bruce Glover (Mull), respectively (because the film went slightly over budget and they could not afford to pay the original actors who played the monsters to return and be in these additional scenes).
The film debut of James Karen.