The Joker

The joker is the arch-nemesis of Batman.  He is portrayed as a master criminal whose characterization has varied.  In some points of view, he is an intelligent psychopath with a warped, sadistic sense of humor.  In other cases he is portrayed as an eccentric prankster.  Some origins say that he fell into a chemical bath, giving him the appearance of a clown.  The Joker is known for his eerie smile and diabolical laugh.  Whenever in pain, he laughs uncontrollably to avoid feeling it.  This is something that many of us do to hide the fact that we're hurting or even to try and convince ourselves that we're not.