How we cite our quotes: All quotations are from The Dark Knight.
Quote #1
BANK ROBBER 1: So why do they call him the Joker?
BANK ROBBER 2: I heard he wears make-up.
BANK ROBBER 1: Make-up?
BANK ROBBER 2: Yeah, to scare people. You know, war paint.
In this case, the most important thing about the Joker, the only thing that matters, is what he looks like. We know everything we need to know about this guy just by looking at his face.
Quote #2
NATASHA: What if District Attorney Harvey Dent is really the Caped Crusader?
HARVEY DENT: If I were going out at night, someone would notice.
Harvey's basically saying that, in order for Batman to be Batman, he can't have a normal relationship with anyone out there. He's probably right, which is why it takes his fiancée dying—cutting off his relationship with the person he cares for the most—to fully turn him into Two-Face.
Quote #3
GORDON: What's he hiding under there?
He asks this question about the Joker, but not about Batman, which is interesting. Batman started out breaking the law, just like the Joker did, and yet Gordon saw something there that separated him from other criminals. Seriously, the Joker's ripping off mob banks when Gordon says this! Maybe the identities of hero and villain aren't as separate as we think…