The Joker's Wife

The Jokers wife is mentioned in "The Dark Knight" when the Joker threatens Rachel Dawes at Harvey Dent's fundraiser and says "...is it he scars? You wanna know how I got them?" makes a reference to her being a gambler that borrowed from loan sharks who one day scarred her face. He then proceeded to place a razor blade in his mouth and create the scars that shape his mouth. He says he did this to show her how her scarred appearance did not matter to him. The Jokers wife however could not stand the look of his new scarred visage and left him. Thus continuing the downward spiral of Jokers mental stability. However whether or not this incident or character was real remains unknown as the Joker told a contradicting story earlier.