When Mack and Murray do the where are you, they 'borrowed' it from Abbott and Costello in Rio Rita (1929).
Steve Lawrence (Mark Howard) and Buddy Hackett (Murray Gruen) not only play legendary comics, they are legendary comics. The two were both frequent guests on Password (1961), What's My Line? (1950) and The Tonight Show Starring Johnny Carson (1962).
The photo of Doris Gruin and Jessica Fletcher taken during their college days was Angela Lansbury and Anne Meara.
The title comes from the phrase No laughing matter which means a serious situation.