Photograph of Jack Nicholson as the Joker on a black and orange background
copyright DC Comics Inc. 1989 MFG. OSP
The Joker is a well-known comic book character and super-villain, who first appeared in the 1940 comic book Batman, and has been depicted in other comic book appearances, television series and films. Tim Burton directed the 1989 film Batman in which actor Jack Nicholson portrayed the role of the Joker. Nicholson accepted the part under strict conditions regarding his salary and filming schedule, including being off for Los Angeles Lakers' home games. Nicholson was nominated for an Academy Award for his performance. Nicholson said that he was particularly proud of his performance as the Joker, saying "I considered it a piece of pop art."
The Joker is actually Jack Napier, a mob member who is presumed dead after falling into a vat of chemical waste during a shootout. Napier becomes the Joker and terrorizes the city with a chemical, Smilex, that causes its victims to laugh to death. Batman realizes that the Joker is the mugger who killed his parents, and thwarts the Joker's attempt to attack a crowd of innocent citizens with Smilex.
Source: D'Agostino, R. (2009). Esquire the meaning of life: Wisdom, humor, and damn good advice from 64 extraordinary lives. New York: Hearst Books.