The below description is taken from LEGO.com.
There’s nothing funny about The Joker minifigure, LEGO Batman’s arch-enemy. He may look like he’s clowning around but this bad guy is bad news in Gotham City! Once a small-time thief, The Joker fell into a vat of chemicals that turned his skin white, his hair green, and his lips redľ like a crazed clown. His pun-loving crimes are always meant to bring Batman down once and for all.