The Joker (then known as Jack) grew up pretty normal. But later went down a dark path with a gang. He attempted to rob a bank but was stopped by the Dark Knight himself on one of his first nights out. Jack was sent to prison. Jack told his cellmate about his plan and how it should not have been stopped. He just could not understand. Jacks' cellmate then began to taunt him for losing to Batman. That is when Jack went crazy, and he hit his cellmate against a wall with pure anger and insanity. Jack had to be transferred to Arkham Asylum. There he became even more angered and obsessed with the world, more specifically, Batman. Later, Jack met Harleen, a nurse who wanted to help him become better. She told him he should smile a little more, be happy, and not take everything so seriously. Which Jack took completely wrong. It was not long after that moment Jack broke out, got weapons, and began coming up with a new plan to rob a bank, but not before he kissed Harleen and said: "I'll be back soon."
Jack stated thinking; it was no longer about the money, it was about getting back at Batman, crime lords, and leaders of Gotham. Jack stated thinking about what Harleen said. So, to make her proud, he picked up a knife and carved into his face. That way he'll always be smiling, no matter what. He just started laughing and could barley stop. Jack came up with the persona, a person who tricks, fools, and kills for fun. Jack was now the Joker. He was ready to become the reckoning of Gotham City and teach those, even those with great souls, can turn and have a terrible downfall. Joker became a well known name in Gotham. He picked out some guys to help on his heist, explained the plan, and got prepped. Que The Dark Knight.