Naturally, the figure has become a popular American sports mascot: Michigan State, San Jose State, Case Western Reserve, and the University of Tampa are among the college teams that go by the name Spartans, and Wikipedia lists nearly 100 high schools, day schools, and private academies whose teams compete under the title as well.
Over time, the term has also evolved to the lower-case “spartan,” which connotes highly disciplined, brave, and austere.
Spanish for “The Cockroach,” this is the title of a Spanish narrative folk song that became hugely popular among Mexicans during early 20th-century Mexican Revolution. Adapted many times with alternate lyrics of a topically political or satirical, today it even constitutes the tune of car horns.
That Yossarian hears the two gunners singing it suggests how happy they are that he abandoned the bombing mission over Bologna.