Boris Karloff only really played Dr. Jekyll in this film. Once the makeup transformation scenes were over, stuntman Eddie Parker did every scene as Mr. Hyde. This was even tipped off to audiences through publicity stills for the film, which showed both Karloff and Parker in makeup standing next to each other.
Unlike other versions of Dr. Jekyll & Mr. Hyde, this time Jekyll is pretty evil in his own right. He seems to have no qualms about deliberately becoming Mr. Hyde so he can commit a murder.
Despite clearly being a departure from the usual Jekyll/Hyde story, two classic characters are referenced. The victim of Hyde in the opening scene is Dr. Poole. In previous versions, Poole is the name of Jekyll's butler. Jekyll also mentions a Dr. Lanson, who is clearly a reference to Jekyll's good friend Dr. Lanyon
In Britain it was given an X certificate though it later played on children's television.
Several of Frank Skinner's music cues are re-used here from the 1948 "Abbott and Costello meet Frankenstein" and can be heard throughout the film.