While walking through Boot Hill, Nobody points out to Beauregard that one of the names on a gravestone is Sam Peckinpah. That same year, Clint Eastwood, in High Plains Drifter (1973), had a Boot Hill scene that included Sergio Leone's tombstone, as well as a number of others.
Composer Ennio Morricone spoofs his own earlier Sergio Leone-helmed "Man with No Name" film scores with an over-the-top soundtrack, including shrill choral voices and a warbling whistle interwoven with a tinny recurring passage from Richard Wagner's "Ride of the Valkyries". Also the soundtrack reuses part of "Frank"'s theme from Once Upon a Time in the West (1968) for the shootout sequence.
The title is a famous quote of "The Odyssey", canto 9, when Odysseus tricks Polyphemus into believing his name is "nobody".