Cosmo

Few characters can claim the distinction of debuting in the second issue of one of comics' most legendary titles, but Cosmo holds that rare honor — introduced in Detective Comics #2 in 1937 by none other than Jerome Siegel and Joe Shuster, the creative duo who would soon reshape the medium forever. A genuine Platinum Age original, Cosmo kept remarkable company in those early pulp-flavored pages alongside the likes of Slam Bradley, Bruce Nelson, and Speed Saunders, rubbing shoulders with some of DC's earliest adventure stalwarts. With 35 catalogued appearances and four recognized key issues to their name, this is a character whose modest footprint belies a genuinely significant place in the prehistory of the American comic book — a collector's quiet discovery hiding in plain sight across one of the hobby's most storied titles.