Joker

Joker is a supervillain and archenemy of Batman.

Personality
The Joker is a dangerous and psychopathic criminal. Although he looks like a clown, he is never to be underestimated. Cruel, sinister, manipulative and above all completely insane, the Joker has proven multiple times to be the Batman's greatest foe.

Appearance
The Joker is a tall, slender man, with pure white skin and a head of bright green hair falling down in a mop style. His most distinguishing feature however is his massive and wide smile that is constantly on his face, giving him a sinister sort of appearance at all times. He is most commonly seen wearing a purple suit with a flower on his lapel, skinny leg pants, a skinny purple tie and a silver chain at his waist.

History
The origins of the Joker are currently unknown.

Almost immediately after the formation of The Team, Superboy and Miss Martian were left alone in Mount Justice to settle into their new base and home. Superboy, however, began to see illustions of a boy named Snapper Carr rushing to the computers and calling for help, saying that he had inadvertently allowed someone dangerous into the Justice League's headquarters. Unnerved by this specter Superboy was then shocked to discover that the person who had been let in was the Joker.

Superboy and Snapper are eventually captured by the Joker, and it is only when the Justice League arrives that Superboy is able confront the Joker properly. Joker however unleashes an army of joker-ized monkeys, who attack Superboy and the League. During the battle Superboy begins to realize that there is something off about the situation, the Joker and in particular about the League.

It is revealed that images of the Joker in Mount Justice had occurred long before and, the Joker, Snapper, the monkeys, and the League were all illusions created by a psychic G-Gnome based on events from long before. This G-Gnome had been responsible for educating Superboy during his developmental stages. After Superboy and his teammates left Cadmus, the G-Gnome, missing Superboy followed him to the new HQ in the hopes of being close to his former pupil/master. With the G-Gnome no longer attacking Superboy, the Joker illusion vanished and the G-Gnome was returned to Cadmus by Red Tornado.