Pat O'Brien acted alongside James Cagney in a number of films during the same time that Cagney's The Roaring Twenties came out. While O'Brien wasn't in that movie, he was in most of Cagney's pictures surrounding it.
The legendary Pat O'Brien had been acting consistently since he began doing plays in the 1920s. This "Happy Days" episode was one of his very last acting jobs.
The title is derived from the classic gangster picture The Roaring Twenties (1939) starring James Cagney and Humphrey Bogart.