Jester is the heroic counterpart of The Joker that appeared in Justice League: Crisis on Two Earths.
Little history is known in the story about the Jester other than he had a pet monkey named Harley. He and Lex Luthor broke into a building controlled by the Crime Syndicate. He helped Luthor steal the quantum trigger, a device that allows people to travel into different universes. An alarm set off in the building sent two villains in pursuit of Luthor and the Jester. The Jester stayed behind, sacrificing himself so that Luthor could escape (and against Luthor's objections.) The Jester was attacked moments later by an evil version of Hawkgirl, and J'edd J'arkus (the evil counterpart to the Martian Manhunter.) The Hawkgirl doppelganger plunged a fiery sword into the Jester's chest, making an apparently fatal wound. The Jester then took a spherical bomb out of his pocket, and set it off. From the street below, Luthor watched the floor the Jester was on explode. The explosion killed the Jester, J'arkus, and apparently the Hawkgirl counterpart.