Secret Scars
Even though he's been in the limelight for years, fans always wondered how he got the scar on his mouth. It fit perfectly for his performance as the Joker, but in real life, no one knew. Was it a cleft lip? Maybe it resulted from a childhood accident? Or maybe, was there something more sinister in Phoenix's past that he wouldn't feel comfortable revealing?
A Mark of God
As it turns out, that was the way the actor was born. Technically speaking, the scar is a microform cleft, which is the easiest case of a cleft lip. However, the actor frequently refers to it as an "act of God." He explained that before he was born, his mother felt a sharp pain, and the family attributed that pain to his mystery marking.