While it has been well documented that Henry Hull objected to Jack P. Pierce's original makeup design for the werewolf, producers were also concerned that Pierce's makeup effects would push the boundaries of censorship in the United States. Producers asked Pierce to tone down the zoomorphic qualities of the werewolf transformation scenes and asked him to make the werewolf appear more human in nature in order to gain approval of the censorship board. Pierce's first design for the creature would later be put to effect in The Wolf Man (1941).
The "original theatrical trailer" provided as a bonus feature on the DVD is actually the re-edited 1935 trailer, with only Henry Hull and Valerie Hobson identified by name, and a Realart re-release title card prepared for the 1951 re-issue. Scenes with Warner Oland are prominently featured but his name never appears, a typical attempt to disguise the age of the film, since Oland had been dead for many years by the time it was re-released.
The werewolf howl used in this film is a combination of Henry Hull's own voice and a recording of an actual timber-wolf. The result is generally thought to have a far more realistic result than in any subsequent werewolf films, including 1941's "The Wolf-Man."
Pre-release publicity material lists Reginald Barlow cast as "Dr. Phillips", scripted as a specialist whom "Dr. Glendon" privately consults after being afflicted with "lycanthrophobia"; this detail, however, was bypassed in the finished production (if indeed it was ever filmed at all), most likely because it would be totally against the established "solitary" character of "Glendon" to do so. At any rate, Barlow was "re-assigned" the uncredited role of the caretaker Timothy.
The trivia item below may give away important plot points.
The theatrical trailer on the Universal DVD contains a brief shot of Dr. Glendon in werewolf form slashing Dr. Yogami's face with his claws as they fight in the laboratory. This shot is not seen in the finished film, although we do get to see Dr. Yogami's slashed face at the end of the scene in the film.