Star Tony Curtis with author Peter Golenbock revealed in Curtis' autobiography "American Prince: A Memoir" (2008) that he became heavily addicted to cocaine during production of this picture and would remain so for the next decade.
Debut produced cinema movie screenplay for both of the film's writers Wesley Lau and Tamar Simon Hoffs.
The film's Lepke (1975) title refers to the nickname of the central character, gangster Louis Buchalter. The name is a shortened abbreviated diminutive version of the name "Lepkeleh" that his mother Rose Buchalter gave him. "Lepkeleh" is a Yiddish word and translates into the English language as "Little Louis".
Photographs of both real life gangsters and the actors playing their screen personas appeared on black-and-white film posters for the movie. Mobsters both real and reel seen on the movie posters included Lucky Luciano, Vito Genovese, Albert Anastasia, Louis Lepke (Louis 'Lepke' Buchalter), Gurrah Shapiro, Bugsy Siegel, Dutch Schultz and Frank Costello.
Tony Curtis was widely considered too old for the early scenes.