Several key cast members in the film are uncredited and their identities remain unknown, most notably the cat-farming neighbor, "Goof", as well as the detective, the skinny morgue attendant, and Maria Altura, the woman who Dr. Meirschultz brings back to life. The identity of the actress who doubles for Altura for scenes that require nudity has also not been identified.
Author and historian Bret Wood has argued that the backyard cat farm in the film was a real, illegal operation in somebody's backyard in a Los Angeles suburb. He also suggests that the morgue was found or rented, rather than a set built by the filmmakers.
A few of the intertitles comment on the action in the film, as they were used in silent films. Five of them describe various mental illnesses: Dementia Praecox (now called Schizophrenia), Paresis (Neurosyphilis), Paranoiac (Paranoia), Manic-depressive Psychoses (Bipolar Disorder), and Manias.
Because Don Maxwell doesn't know what to put in the syringe he puts in water saying that it would not be harmful, injecting water into a vein however would cause red blood cells to rupture which could, depending on the type and amount of water, be very harmful.
Marian Constance Blackton is sometimes reported, incorrectly, as appearing in male drag as the neighbor who catches and breeds cats. She plays a female neighbor who is questioned by the detective.