In spite of Boris Karloff and Bela Lugosi receiving top billing, neither actor would dominate the story-line. Character actor Stanley Ridges would take center stage.
Despite problems with Boris Karloff, who steadfastly insisted that the studio comply with the union-mandated eight-hour day (a rule largely ignored, except when a major star demanded compliance), director Arthur Lubin was able to bring the picture in on schedule and $5,000 under budget.
In an interview, Curt Siodmak said of Boris Karloff, who demanded - and obtained - Bela Lugosi's role in this film: "Karloff didn't want to play the dual role in Black Friday. He was afraid of it. There was too much acting in it. It was too intricate." Karloff thus ended up with the part written specifically for Lugosi, inexcusably leaving the Hungarian actor to play a then poorly cast, minor role as an American gangster, instead of being given Karloff's dual role which instead went to Stanley Ridges. In an interesting twist of events, the following year, Lugosi would have the chance to prove how great he would have been in the dual part, as he was cast in a split personality role in Monogram's O Fantasma Invisível (1941). Karloff, throughout his career, proved he was more than capable of playing dual roles.
According to contemporary publicity reports, Bela Lugosi was put under hypnosis by technical advisor Manly P. Hall to make his death scene more realistic and harrowing. This was later disproven.