The character of "John Cassidy" is allegedly based on playwright Sean O'Casey (his name is an Anglicization of O'Casey's), but Rod Taylor, playing the part, bears no resemblance to the famous writer. The real O'Casey was a diminutive man with poor eyesight who always wore thick glasses and kept out of violent encounters. He was a working-class man of strong intellectual gifts and fierce political views, and in reality was, at the time of the events depicted, about fifteen or twenty years older than "Cassidy" is supposed to be.