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.
Zeppo tells Mike that he is going to use phrenology to tell many things about him by reading the bumps on his head. He also says Gypsies originated the "Art of phrenology". Developed in the late 18th and early 19th centuries in Europe, phrenology was considered a science that could predict mental traits, however by the 1840s was widely recognized as a pseudoscience.