The character originally appeared in various Silver Age DC Comics advertisements, and was used to promote DC's entire line of comics. He had a cartoonish face, wore a mortarboard, had stick figure lines for his arms and legs, and a body that consisted of the DC Comics logo.
In the late 1980s, Johnny DC hosted a DC promo page called "DCI with Johnny DC" which appeared in many comics of the era. Like Marvel's "Bullpen Bulletins"—and DC's previous incarnation, the late 1970s/early 1980s Daily Planet feature—"DCI with Johnny DC" featured miscellaneous DC news items, often spotlighting certain books or creators, and also included a partial checklist of current DC titles.
In the mid-1990s, Johnny DC appeared in the satirical special Sergio Aragonés Destroys DC. He's shown as having become disillusioned with the modern direction of DC's superhero comics, criticizing the various members of the Justice League and accusing them of having changed for the worse.
In 2004, Johnny DC was revived and redesigned, as a mostly-silhouette cartoonish child. His name is now used as the name of DC Comics' imprint of comics marketed primarily to children, approximately ages 8–13. The line consists primarily of books based on Warner Bros. and Cartoon Network animated TV series. These have included series that began as animated features (e.g. Scooby-Doo, Looney Tunes, and The Powerpuff Girls) and those based on DC Comics superheroes (The Batman Strikes!, Teen Titans Go!, Legion of Super Heroes in the 31st Century, and Justice League Unlimited). The letter columns of these titles are supposedly edited by Johnny DC.
In April 2008, Johnny DC imprints has been discontinued and replace it with DC Comics "swirl" imprints.
A female version of the character appears in Ambush Bug comics as "Jonni DC, Continuity Cop". In early appearances, she investigated Ambush Bug's casual violations of DC Universe canon. In the 2008 miniseries Ambush Bug: Year None, Ambush Bug is called in to investigate Jonni DC's apparent murder. Later she rises again as a sedate, controlled Black Lantern.