When Davy Jones puts the stethoscope up to the safe to try to crack it open, he hears a snippet of "The Last Train to Clarksville".
Peter Tork says that the word Gypsy makes him think of Ethel Merman, who played Mama Rose Hovick in the play Gypsy on Broadway in 1959.
Musical number featured in this episode: "I'm a Believer".