The original team-up between alternate versions of the same superhero occured in this issue of The Flash. The helmet-wearer on the right is Jay Garrick, the original Flash from the 1940s, the Golden Age of comics. Like most costumed superheroes, his comic went into decline after World War II and was eventually cancelled. In the late 1950s, the Barry Allen Flash, on the left, inaugerated the Silver Age of comics, and once again, the old reliables (Superman, Batman, Wonder Woman) were joined by hordes of improbably talented people with strange powers and stranger sartorial ways.

This issue revealed that two versions of earth existed in alternate universes. The story set the stage for numerous crossovers to come, as DC's Golden Age and Silver Age heroes and villains regularly teamed with their counterparts. More and more universes were added to the comic cosmic jenga-pile, until the 1980s, when a comic-book event called Crisis on Infinite Earths collapsed the structure. Crisis left only one new universe that contained the most marketable heroes, and a more Marvel-influenced sensibility.