In an August 2013 Entertainment Weekly interview, Joss Whedon said that his then-upcoming ABC/Marvel comics television show Agents of S.H.I.E.L.D. (2013) would be "basically a TV series of 'The Zeppo', which was a very deliberate deconstruction of a Buffy episode in order to star the person who mattered the least. The people who are ignored are the people I've been writing as my heroes from day one."
The structure and concept of this episode (which for the most part follows Xander on what in another episode would be his subplot, while the series' more conventionally main characters are relegated to the background) is an homage to Tom Stoppard's 1967 existentialist play 'Rosencrantz and Guildenstern Are Dead', which follows the action of two relatively minor characters from William Shakespeare's "Hamlet" while using the actual main plot and characters from 'Hamlet' as occasional background and diversion.
"Zeppo" (Herbert Manfred) Marx was the fifth and youngest of The Marx Brothers, after Chico Marx, Harpo Marx, Groucho Marx, and Gummo Marx. Although he was a performer (unlike Gummo), he was rarely given much comedic material, usually playing the "straight man" in the Marxes' plays and movies instead - hence Cordelia's insult to Xander that he is inessential to Buffy and the gang and therefore "The Zeppo" of the group. Zeppo Marx stopped appearing in films after Duck Soup (1933), and formed a theatrical agency with Gummo.