Stage manager Maurice Cass vows that the opera will go on "even if Frankenstein walks in!" Audiences were well aware that this in-joke referred to star Boris Karloff, who was in the theater at the time.
The unique billing listed Warner Oland vs. Boris Karloff above the title. Karloff had turned down the title role in Werewolf of London (1935), which would have pitted him against his current co-star. The part was ultimately played by Henry Hull.