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 well-known "Wolf Man" makeup used on Lon Chaney Jr. was actually created by Universal Pictures makeup designer Jack P. Pierce for Henry Hull in this film. After makeup tests, Hull declined to wear the makeup, citing his dislike of the time-consuming makeup application. A less hairy version was then devised by Pierce, and it is this version that is seen in the film. A still photograph of the original test makeup survives, however, and has been published.
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."
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.