Filming was interrupted due to financial difficulties, and because of that the script was not filmed as written. Whole segments of the script involving flying saucers and a Golem were never carried out, as the result of sorely lacking funds.
US distributor Samuel M. Sherman chose "La Marca del Hombre Lobo" for his pre-booked "Frankenstein" title, passing on the opportunity to showcase this film, which actually features a "Frankenstein" monster. He also believed that this film's European distributor ripped off his Al Adamson title Dracula vs. Frankenstein (1971).
Paul Naschy's third performance as Waldemar Daninsky (the second that was seen on theaters, being that the previous "Las noches del hombre lobo" was an unfinished film) and the only one that the character was a supporting role. The fourth would be Fury of the Wolfman (1972), although this film was released after the fifth The Werewolf Versus the Vampire Woman (1971).
The werewolf, played by Paul Naschy, has no specific origin in this film. It is assumed that the events in this film are continued from the ending of Frankenstein's Bloody Terror (1968) ("The Mark of the Wolfman"), in which Naschy, as Waldemar Daninsky, was transformed into a werewolf through the bite of a werewolf named Imre Wolfstein. Strangely, The Wolfman was killed in the same exact manner in that first film, but the aliens surgically remove the silver bullets to revive him.
Originally slated to be called "The Man Who Came From Ummo", referring to Michael Rennie's spaceman character.