3. ACTION COMICS #252 (1959)

This issue of Action Comics featured the debut of Supergirl and it has become one of the most parodied and popular Silver Age comic covers of all time. At the time, the idea of another character with Superman’s powers seemed unfathomable, but in the years since, Supergirl has become almost as popular as the Man of Steel himself.

As the years went on, Supergirl’s skirts got shorter, her bust line expanded, and she began to resemble a perverted fetish fantasy for sex-starved comic fans rather than the memorable character she was in her debut. Not that there's anything wrong with that.