Originally, Lon Chaney Jr. was to play both the Wolf Man and the Frankenstein Monster, but the producers decided the make-up demands and schedule wouldn't permit this. Late in life Chaney stated in an interview that he did, however, play both monsters in the film. He may well have been referring, correctly, to Bud Abbott Lou Costello Meet Frankenstein (1948) where he briefly doubled Glenn Strange after Strange broke an ankle throwing a woman through the laboratory skylight near the end of the film. You can actually see Strange stumble but keep upright after the throw.
The dialogue spoken by the Monster in the film was edited out before the film's release. His dialogue in the film spoke of his desire to control the world but Universal executives feared that World War II audiences would find it too close to Adolf Hitler's own rhetoric.
The Frankenstein Monster, played by Bela Lugosi, is mute in this film, even though Boris Karloff's monster spoke in the earlier The Bride of Frankenstein (1935). Interestingly, Lugosi had refused the role in the original Frankenstein (1931) because he would have had no lines. When Lugosi accepted the part in this film, the original script contained dialogue for the Monster, which was later edited out.
When The Monster's dialogue was deleted (see Alternate Versions), also removed were any references to The Monster being blind - a side-effect of Ygor's brain being implanted into The Monster at the end of The Ghost of Frankenstein (1942). As a result, Lugosi's sleepwalker-like lumbering gait with arms outstretched is not explained and became the subject of ridicule. It also established the Frankenstein Monster-walk stereotype.
Several photos exist showing the deleted scenes (the fireside chat between the Monster and Talbot beneath the icy catacombs of the castle for instance; where Talbot & the audience learn that the Monster is still blind). This has been confirmed by several sources, including screen writer Curt Siodmak. In the mid-'80s a search was made through the Universal Studio vaults for a print or negative of the uncut prerelease version. As of this date, it has not yet been found.
This is the first Frankenstein movie to not feature a "Dr. Frankenstein." Lawrence Talbot seeks Dr. Frankenstein for help, but never does meet him. However, there is another "Frankenstein": Ilona Massey's Baroness Elsa Frankenstein, possibly named after Elsa Lanchester who played both Mrs. Shelley and the Female Monster in The Bride of Frankenstein (1935). According to the opening scene of the same "Bride" movie, the Monster's name is also Frankenstein within this film continuity, regardless of what it says "in the book."
When Larry Talbot discovers a photo of Elsa Frankenstein, you can see the Monster's mouth moving, but without sound coming out. Most scenes that included the Monster's dialogue were cut completely from the film or dramatically shortened. Here, Bela Lugosi's voice track was simply erased.
Stuntman Gil Perkins doubled for Bela Lugosi in the action scenes, as well as the scene of the Monster being released from the ice. In the climactic fight scene, Eddie Parker doubled Lon Chaney Jr. as the Wolfman, while Gil Perkins took over as the Monster. Based on interviews given years later, Perkins may have also doubled Chaney's Wolf Man in the chase scene through the woods into the castle ruins. Some film scholars insist Eddie Parker appears as the Monster in a handful of shots in the climax.
The film was shot during WWII, amid a notorious anti-German public campaign by the United States government. Screen writer Curt Siodmak, a German Jew himself who had fled his country after hearing anti-Semitic speeches there in 1937, deliberately changed the location of Frankenstein's castle from Germany to the fictional "Vasaria." "Vasaria" translates loosely to "water place" in German, obviously correlating the dam, waterfall and hydroelectric turbine that are integral to the film.
The dog (Bruno) in the film is a German Shepherd named Moose, whom Lon Chaney Jr. adopted from the Universal Lot just after Moose's earlier appearance as the wolf that attacks Lawrence in The Wolf Man (1941).