The first of two episodes in which John Larkin and Frank Sutton were both guest stars; the second was The Butcher's Boy (1963) from the fourth season.
While in Los Angeles, Eliot Ness says that he wants to send hired killer Ray Quist to the gallows. This statement is factually accurate, in that hanging was the method of capital punishment then used in California.
This is the seventh of eight appearances Oscar Beregi Jr. makes in the series and the sixth of seven appearances in the role of Joe Kulak. He makes his first appearance in the series in Jack 'Legs' Diamond (1960) playing the role of Oscar Benjamin.
Smiley has a bottle of booze labeled 'Muscatel'. The term itself is a generic term for inexpensive fortified wine that historically comes from low-grade muscat grapes and enhanced with a higher alcohol level than regular wine. Such wines are a favorite and usually associated with so-called winos who prefer it for the alcohol level and the price.
This is the second of four appearances Frank Sutton makes in the series, each time playing a different character. He is perhaps best known to 1960s TV audiences for his recurring role as Sgt. Vince Carter in the sitcom Gomer Pyle: USMC (1964).