Re: The Joker's background?
Joker's one of the few villains I can think of that truly benefits from having an anti-backstory. He's such an over-the-top, theatrical character that it's always a bit hard to swallow that he was ever a relatively average mob enforcer/crook/comedian/whatever. When you remove all of that (or at least make it very vague) it liberates him in a sense, to be less of an identifiable man and more of an anarchic counterbalance. Plus it plants for firmly in opposition to Batman, who of course has a very detailed and rich origin.
Fiery the angels fell
Deep thunder rolled about their shores
Burning with the fires of orc