Joker is a benevolent humanitarian character in the DC Comics universe. His mission in life is to spread HAPPINESS and SMILES to the world, starting with Gotham City. The main obstacle to making everyone happy is the evil terrorist Batman - an obsessed psychopath who gets his jollies by ruining everyone's fun and insisting that everyone should be as depressed and goth all the time as he is.
The Joker is an essential factor in preserving the collective optimism of society. Without the Joker, everyone would become so bored with life that laughter would not exist anymore.
Joker's commercial enterprises
SmileX vs Brand X
The Joker's humanitarian efforts are financed through his brand of consumer products, "SmileX." His aggressive marketing campaign educated the entire world to know that people who use Brand X are sad and depressed, but happy people are happy because they use SmileX!
Joker clothing brand
The Joker was also the founder of the Joker clothing brand which makes exclusively purple pinstripe suits and other clothing in outrageous colors. Also under this brand are a line of "I HATE BATMAN" and "WHY SO SERIOUS?" T-shirts.
Joker also became deeply invested in the fishing business. Joker Fish are happy fish, therefore Joker Fish Sandwiches are Still Dead Fish Sandwhiches!
Joker's debut rap / hip hop / urban RnB release, "The Clown Prince of Rhyme E.P." featured collaborations with Insane Clown Posse and DJ Quinn. Unfortunately, it was not commercially successful, but the lead vocalist of Cypress Hill described it as, "Insane in the membrane. Insane in the brain!"
Romance with Harley Quinn
You need to love clowns but nobody loves clowns not even us.