The Joker was born as a very small, bald and toothless baby, by a woman who was previously pregnant for 9 months. He was the first and only child of his parents. A child born out of love and desire.
His parents were very religious and family values meant the world to them.
As any child, born into a loving family, the Joker was adored and cherished.
But as he grew up, his parents noticed that something was a bit odd with their little precious one.
Joker showed early signs of high intelligence and extrem curiosity.
His genious like mind made him question everything, and while boys of his age were disasembling toy cars to see what makes it run... Joker was more interested to see what makes a cat or a dog run... So, very early in his childhood, he started opening up different animals to see what's inside, what makes them alive and what makes them dead ( how many punches, what kind of a weapon, etc ).
No one know of this hobby of his. His intelligence told him that people wouldn't understand.
As he was growing up, learning more about the world and him self, he discovered that he was way smarter than everyone around him. Soon it made him bitter, because he found him self being bored by people. There was absolutely nothing interesting coming out of their mouths. More than often he would be able to predict what they would say, and their simple and boring minds began to frustrate him. No one could excite him, nothing made him feel the rush of adrenalin in his body, and the emptiness that consumed him started corrupting his twisted mind even more.
But, when he was a teenager, he discovered that there was something that made him smile: shocking people. Shocking them by the things he would say or do. So, he started loving how easily he would make someone uncomfortable or creeped out. And that finely made him feel... It challenged him to push his own boundaries.
By this time, his parents were pretty much sure that there was something really wrong with him and they prayed more and more.
Every time they would get scared by their little boy, they would get on their knees and asked God for an advice. Joker loved seeing a mixture of negative emotions on their faces: worry, terror, shock... stupidity. And one day, when they were staring at him like that, after he brought the neighbours puppy into the house and killed it in front of them, the look on their faces gave him a rush of pleasure, and he couldn't resist but to ask: "Why so serious?" The question and the whole situation made him burst into laughter. Then and there he decided that it was his favourite question of all, because he saw it freaked them out, just the way it should.
That was the day he killed his parents and moved out of the family house.
He moved to Gotham City, a place with a bad reputation, with darkness that matched the one in his mind and a place that for some reason promised so much.
From then and there, Joker lived for and from crime, thinking of new and exciting ways of shocking people.
In his attempt to push further, one day he decided that his apearence was way normal. And he disliked everything normal, which made him dislike his own reflection in the mirror. So he decided to make him self look pretty.
He bleached his face which almost burned of his skin, but he didn't care. He dyed his hair green, which was defined by psyhology as a soothing and restful colour and he thought it would be an interesting contrast to his character and to the things he did. It amused him a lot.
And also, he thought he should keep smiling. He learned that there was nothing that would put people unease so much as a fake smile. So he took a knife and gave him self a permanent smile.
He decided that a smily face is a good balance to a dark monster inside him.
He hated people for their stupidity and their simple minds. He noticed that they were afraid of truths so he took it upon him to tell the dark, unpleasant truth of existence when ever he could. But he also liked to tell lies, made up stories, to confuse people, to mess with their minds, to laugh, to enjoy the supremacy he had over them.
He didn't believe in goodness, he saw beyond that. He knew people were just animals trying to adapt to their surroundings and survival often required certain behaviour. He was just so much more intelligent than others, he saw everything for what it really was: hopeless.
Sometimes a person doesn't become, it's just born as a psychopath. Not having a reason often scared people the most, so he decided to never give them a reason or the answer to the questio: why?