 Joker holds Batmans funeral in the Ace Chemical Plant. In the  comics this is where Jokers origin takes place. He was a smalltime  crook who, during a robbery that was foiled by Batman, fell into a  chemical vat in the Ace Chemical Plant that died his hair green and  bleached his skin white as makeup. Thus he became the Joker. Whether  or not this story is true is unknown, although a similar origin was  used in the "Batman" (1989) movie and has now been referenced in  this animated series.