A villain of the Batman universe, first appearing in Batman #1 (1940). He is considored to be the Caped Crusader's arch nemesis. His title is the "Clown Prince of Crime".
The Joker's real name is unknown, though
according to the first movie starring Nicholson, it might of been Jack Napier. The catalyst of his insanity has different tellings:
Originally a failed comedian, coerced into crime
after the deaths of his wife and unborn child. Disguised as the "Red Hood", he failed to steal from Monarch
Playing Cards. Running from Batman, he fell into a waste pool by the Ace Chemical Processing.
Surving the accident, it coloured his hair green, bleached his skin white and deformed his mouth into a red smile. Using eccentric weapons like acid spilling flowers and static joy-buzzers, he sadistically amuses his victims before he murders them. Other schemes include bribery and terroism.
The sidekick and former pyschiatrist of The Joker is Harley Quin (a.k.a Harleen Quinzel). She
accompanies and supports her love interest in his crimes in Gotham City.