Explaining why he took the role of Frankenstein in this film, David Carradine said "I started that picture two weeks after I walked off the Kung Fu (1972) set, and that was essentially my image, the "Kung Fu" character, and a lot of people still believe I'm that guy. The idea actually was: No. 1, if you walk off a television series, you better do a movie right away or you might never get to do one. And the second thing was to do something right away that would create the image of a monster to get rid of the image of that little Chinese guy that I'd been playing for four years. And, you know, it did kick-start my movie career."
The custom-built cars used in the film did not run most of the time, so they had to be pushed down hills in order to get them to move at all. Moreover, the cameras used to film the cars were undercranked in order to perpetuate the illusion that the cars were going faster than they actually were.
According to Roger Corman, several of the custom-built cars featured in the film were later sold to car museums for considerably more than it cost to build them.
Both David Carradine and Sylvester Stallone did much of their own driving in this film. In addition, producer Roger Corman drove in scenes that were shot on public streets, since the custom-built cars that were used in the film were not street legal and the film's stunt drivers did not want to be caught driving them by the police.
David Carradine refused to wear leather, so costume designer Jane Ruhm had to make Carradine's iconic black outfit out of another fabric that looked just like leather.