Dwight Frye appears as 2 different characters. First as one of the villagers who destroys the Frankenstein castle at the beginning of the film. Later in flashbacks to the original Frankenstein where he played Fritz, the hunchbacked assistant to the original Dr. Frankenstein.
Ralph Bellamy had previously played a member of law enforcement who hunts a murderous monster. The first film was The Wolf Man. In both movies Lon Chaney Jr. plays the monster.
Lionel Atwill's character (Dr. Bohmer) is responsible for ensuring Ygor's (Bela Lugosi) brain is switched with that of the monster (Lon Chaney Jr.) making him far more dangerous than he was before. In Man Made Monster Atwill plays a mad doctor who makes Chaney Jr.'s character dangerous via electricity (which originally brought life to the Frankenstein Monster)
Boris Karloff, then acting in the hit Broadway show which became Arsenic and Old Lace, had no interest in working on the film. Producer George Waggner wisely decided to retain Karloff's make-up out of fear that the public would not accept any change in the monster's appearance.
Chaney would play the Monster a number of times later: footage from this film appears as stock shots in House of Dracula; he doubled Glenn Strange for three shots in Bud Abbott and Lou Costello Meet Frankenstein when Strange twisted his ankle; he played the role in a half-hour version of "Frankenstein" on TV's Tales of Tomorrow; and he appeared (masked) in two comedy sketches with Bud Abbott and Lou Costello on a 1952 The Colgate Comedy Hour show.
During breaks in filming, Lon Chaney Jr. would often treat child cast members to ice cream.
It was reported that the rubber headpiece used for the Frankenstein monster make-up was very uncomfortable for Lon Chaney Jr. to wear. It sat directly on his forehead and he constantly complained. Once he asked for it to be removed. Angry and frustrated when no one listened, he ripped it off himself, tearing open a bloody gash in his forehead. Production on the film was shut down for a couple of days.
Lon Chaney finished "The Wolf Man" on November 27, 1941, then started this film on December 15, finishing on January 15, 1942. Release took place on April 3.
Part of the SON OF SHOCK package of 21 titles released to television in 1958, which followed the original SHOCK THEATER release of 52 features one year earlier.
The first draft of the script was written by Eric Taylor was considered too depressing. The original Taylor treatment brought Wolf von Frankenstein back into play, as well as Ygor, plus a misshapen hunchback, Theodor. Ygor's plan was to create a vengeful mob of society's rejects, ala Freaks, led by himself, with the Monster as brute force. A rewrite was ordered and given to veteran writer Scott Darling who retained the fundamental scenario but made significant changes.
Ygor and the Monster weren't the only characters who came back from the dead. Michael Mark and Lionel Belmore, who play the two council members murdered in Son of Frankenstein are back as council members in this one, seemingly none the worse for wear.