The Joker is a fictional DC Comics villain, widely considered to be Batman's arch-enemy and one of the most well-known villains in comic book history. The idea was conceived by Batman inkerletterer Jerry Robinson (while on staff under Batman creatorartist Bob Kane), the Joker first appeared in Batman #1 (1940). Originally conceived as an evil "court-jester" type, the character was rejected by studio writer Bill Finger as being "too clownish" however, he later relayed the idea to Bob Kane. Kane, who started out as a "gag" artist, loved the concept and encouraged its production. Mr. Finger found a photograph of actor Conrad Veidt wearing make-up for a silent film entitled The Man Who Laughs (which was based on a novel by Victor Hugo.)and it was from this photograph that the Joker was modelled. The Joker is a humor-obsessed criminal with a clown-like appearance, who likes to kill people with fatal hilarity. Writers have alternatively portrayed him as a goofy trickster-thief or as a serial killer with a warped sense of humor. Recent writers of the Batman comic book series have preferred the latter, and the Joker has been responsible for numerous tragedies in Batman's life, such as the murder of Jason Todd, the successor to the mantle of Robin after Dick Grayson, the injury/paralysis of Barbara Gordon, a.k.a. Batgirl/Oracle, and the death of Sarah Essen Gordon, Jim Gordon's wife. The Joker is regarded by fans and comic-book aficionados as one of the greatest villains in comic-book history and by many the one with the most psychological depth. The Joker has been featured throughout the Batman saga, and has been an enemy of the Caped Crusader in most adaptations in other media. Interpretations of the Joker that have made him well-known to the general public include Cesar Romero's in the 1960s Batman television series, Mark Hamill in the DC Animated Universe and Jack Nicholson's in the 1989 feature film. The Joker (as played by Nicholson) ranks number 45 in the American Film Institute's list of the top 50 film villains of all time. http://en.wikipedia.org/wiki/Joker_%28comics%29

The Origin of the Joker a.k.a. “The Man Who Laughs”. In the Origin of the "The Man Who Laughs," the joker is a young lad and a pathetic victim instead of his usual role as a villain. In this moving melodrama he had a dual role, starring as both Gwynplaine (The Man Who Laughs), and also as Lord Clancharlie, Gwynplaine's father, a Scottish nobleman who has rebelled against King James II in 17th-century Britain. As Lord Clancharlie is being placed for execution in the notorious "Iron Maiden," he asks what will be done with his son, Gwynplaine. King James' cruel jester pulls the boys mouth apart in a grimace, and the king understands that the young boy with a beaming, angelic smile will be given to a notorious band of nomads, the Comprachicos. The Comprachicos purposely disfigure the young boy by carving the corners of his mouth into a fixed, hideous grin. As if what they have done turns into a bad Omen, the Comprachicos are exiled from England, abandoning Gwynplaine in the English countryside during a severe snowstorm burning his facial expression into a permanent one. Plodding through the storm, the youngster comes across a baby girl in the arms of her frozen and lifeless mother. Although the boy doesn't have any reason to perpetuate acts of kindness due to his practically shattered spirit, his heart goes out to this young child, and he rescues her. As he plods through the howling storm with the baby in tow, they are saved by a small traveling troupe of actors who are led by kindly philosopher, Ursus. Ursus is horrified when he sees Gwynplaine's disfigured face, and he realizes that the baby girl, Dea, is blind. They are both adopted by the troupe, and years later Dea, has grown into a beautiful blind girl. A romance of the heart, not of the eyes, develops between Gwyplaine and Dea. Gwynplaine, who has now become a famous performing clown, is finally happy, and fate steps in when Gwynplaine discovers he is heir to a peerage and is summoned back to London. It is there that his life will take a fateful turn when the jester who had persuaded the king to disfigure Gwynplaine and the queen, see an opportunity to continue their mind-twisted torture. MAYBE THEN ALL WILL UNDERSTAND WHY JOKER LOST IT.

As revealed via flashback in "The Killing Joke", the man who became the Joker was a chemical engineer who gave up his job to try to make a living as a standup comedian, which he failed at miserably. With his wife pregnant and desperate for money, he falls in with a gang of thugs who are planning to rob the payroll of the chemical plant he used to work at, with him wearing the disguise of "The Red Hood" -- a two-bit villain used as a fall guy for these crimes. The day before the robbery, the Joker is informed by the police that his wife has died from electrocution in a household accident. The other members of the gang warn the Joker that trying to pull out of their robbery plans would be "unhealthy", so they go through with the caper. In the midst of it, the Batman shows up, and during the scuffle the Red Hood is knocked into a vat of chemicals. When he eventually escapes, he discovers that he's been permanently transformed -- his skin is now chalk-white and his hair emerald green. Unable to take the multiple shocks of his disfigurement, the loss of his family, and being assaulted by the Batman, the Joker's mind finally snaps.

there is a lot of contention on who created the joker without any real answaer just thought id put that point in

One of the amazing features of the Joker is his foggy background. Like in "The Dark Knight," every time he tells it, it is different. The Killing Joke comic is one of the mostly widely excepted versions of his origins, but it is debatable as there are several other tellings as well.

The recent Killing Joke animated movie got mixed reviews, but I thought it was good. Definitely worth a look.

Steve Miller. https://www.youtube.com/watch?v=YZo88P1Ie94