He was best known for his short stories celebrating Broadway as it was coming out of Prohibition. A “Damon Runyon character” usually meant a disreputable person who walked a fine line between both sides of the law. Runyon wrote tales of gamblers, hustlers, actors, and gangsters, with colorful names like ‘Nathan Detroit’ and ‘Harry the Horse.’ His distinctive vernacular style known as “Runyonese” meant a mixture of formal speech and slang almost always in present tense.
Runyon’s fictional world is also known to the public through the musical “Guys and Dolls,” based on his stories “The Idyll of Miss Sarah Browns” and “Blood Pressure.” “Guys and Dolls” was turned into a Broadway musical in 1950, and later was a film (1955). The original Broadway production ran for 1,200 performances and won the Tony Award for Best Musical. The film adaptation starred Frank Sinatra and Marlon Brando.
Here is the opening scene from the 1955 movie: