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.
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, before turning into a "psychotic and badly-drawn" pastiche of 1990s comic book anti-heroes in an attempt to destroy the heroes, only to be defeated when Batman tricks him into saying his name backwards à la Mr. Mxyzptlk.
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 and Looney Tunes) and those based on DC Comics superheroes (Krypto the Superdog, The Batman Strikes!, Teen Titans Go!, Legion of Super Heroes in the 31st Century, Justice League Unlimited and Super Friends, based on the eponymous Imaginext toyline).
A female version of the character appears in Ambush Bug comics from 1986 to 1992 as "Jonni DC, Continuity Cop".