What do Batman, Janis Joplin and Julia Child have in common? If you guessed "They just got their own stamp," you're correct.

As DC Comics continues its celebration of the 75th anniversary of Batman, the iconic hero will again grace postage stamps in a limited-edition set officially unveiled Oct. 9 as the U.S. Postal Service kicks off New York Comic Con with a first-day-of-issue ceremony.

Each sheet of 20 "Forever" stamps -- they're 49 cents each but will remain good even when rates increase -- will features designs representing four eras: the Golden Age, the Silver Age, the Bronze Age and the current New 52 era. There's also a round stamp with the Batman symbol.

Batman is only the latest in a series of DC characters, including The Flash, Wonder Woman, Superman and Aquaman, who have graced U.S. postage stamps recently. And this isn't actually the first Batman stamp, as Linn's Stamp News notes: The DC Superheroes set issued in 2006 included two Dark Knight stamps.

Canada Post last year honored Superman's Toronto roots, and his 75th anniversary, with a series of commemorative stamps.

As we noted last month, there has been a bit of controversy over the issuing of pop-culture stamps, with former Postmaster General Benjamin F. Bailar quitting the Citizens Stamp Advisory Committee, claiming that the USPS's current stamp program "lacks gravitas." While the committee is supposed to choose the subjects for stamps, the Postal Service went ahead with a Harry Potter stamp without consulting them.