Chuck goes to a club called "El Bucho" and dresses up like a Mariachi and performs on stage. In DESPERADO, the main villian is named Bucho, the hero is a Mariachi, and he performs on stage.
The sparring match is a direct parody of the film. The music, the glove colors and the freeze frame at the end of both characters punching are the same. Even the way the characters dance around the ring mirrors Rocky and Apollo's sparing match.
The montage where "Just Dropped In (To See What Condition My Condition Was In)" is playing is a reference to a drug induced trip encountered by "The Dude"