The humor came from seeing someone big and tough who might be gay, or who was too "stupid" to realize that his acts were gender-transgressive.
In real life, he was married for a few years (1937-45), but he seemed to prefer the company of men, such as trainer and manager Frank Bachmann (left). And he was not averse to gender-transgressions: apparently a young Davis Hopper saw him in drag at the premiere of Dodge City (1939).
In 1950, he teamed up with his lifelong friend, another boxer-turned-actor, Max Baer (known as Mad Max, top photo and left), playing the "stooge" who bedevils "straight man" Baer. They starred "as themselves" in four comedy shorts and toured as the comedy team "The Two Maxies."
They remained close friends until Baer's death in 1959. Slapsie Maxie died in 1976.
The Beverly Hillbillies (1962-71). Later he contributed to gay history by producing Ode to Billy Joe (1976), starring Robby Benson as a gay teenager who commits suicide.