The Manster (1959)
Mad Japanese scientist Dr. Robert Suzuki (Tetsu Nakamura) hopes to create a serum that will advance human evolution, but all efforts so far have been less than successful, earlier attempts having turned his wife and brother (who apparently volunteered for the experiment, making them just as mad as he is) into hideously deformed monsters.
Not one to admit defeat, Suzuki—aided by his glamorous assistant Tara (Terri Zimmern)—gives it one last go, drugging and injecting roving US reporter Larry Stanford (Peter Dyneley) without his knowledge. The serum takes effect gradually, Larry becoming progressively more wild and uncontrollable, first succumbing to the pleasures of booze and geisha girls, but eventually turning to murder. As his personality becomes more monstrous, so does his appearance: his hand gets hairy, an eyeball appears in his shoulder, and he grows a second head, eventually splitting into two separate beings.
A wonderfully subversive storyline and a standout central performance from Dyneley help distinguish The Manster from most of its contemporaries; Stanford's insatiable sexual appetite and violent outbursts, Tara's dubious past (I'm guessing that she used to be a hooker), Dr. Suzuki's callous and calculating approach to his 'work', and the unforgettably surreal transformation from man to beast all go to make this film a genuinely freaky and thoroughly enjoyable ride into darker-than-usual 50s B-movie monster territory. (IMDB BA_Harrison)