"“Superman?” Clevinger cried. “Superman?”"

Having misheard Yossarian’s claim to be a “supraman,” Clevinger thinks the captain has referred to himself as the comic-book superhero from the planet Krypton. The character was the creation of American writer Jerry Siegel and Canadian artist Joe Shuster, who had come up with the character in 1932 but did not debut until Action Comics #1 in June 1938. 

Superman received his own self-titled comic the following year (mostly filled with recycled stories) and made appearances in World’s Finest Comics and All Star Comics in the early 1940s.

Superman
Public DomainSuperman

Yossarian and his army buddies might well have seen Superman in the newspapers, where a daily comic strip and separate Sunday series had launched in 1939 and would run steadily until 1966. The image above is from a 1941 cartoon by the Fleischer Studios. At its peak, the Superman comic appeared in more than 300 daily newspapers and 90 Sunday papers, with a readership of roughly 20 million.