Heath Ledger doesn't need an introduction. He made a special place for himself among the hearts of fans and critics, despite a short professional career, with his incredible acting in several movies, most notably, in Christopher Nolan's "The Dark Knight" as the antagonist, the Joker.

Ledger portrayed the character of the Joker to chilling effect, and electrified the audience with the intensity of its personality. Ledger's portrayal of the Joker made "The Dark Knight" one of the most revered superhero movies of all time.

Ledger was posthumously given the Academy Award for Best Actor for playing the Joker as he died from intoxication from prescription drugs before "The Dark Knight" released. The award was received by a grieving cast and crew of "The Dark Knight."

Apart from being one of the finest actors in Hollywood, Ledger was, and is still considered, one of the most respected. As the world celebrates the 37th birth anniversary of the legendary actor, here are some of his most popular quotes as the Joker in "The Dark Knight."

"If you're good at something, never do it for free."

"Why so serious?"

"Let's put a smile on that face."

"All you care about is money. This city deserves a better class of criminal. And I'm gonna give it to them."

"Do you want to know why I use a knife? Guns are too quick. You can't savour all the little emotions. In, you see, in their last moments, people show you who they really are. So in a way, I know your friends better than you ever did. Would you like to know which of them were cowards?"

"Introduce a little anarchy. Upset the established order, and everything becomes chaos. I'm an agent of chaos. Oh, and you know the thing about chaos? It's fair."

"I took Gotham's white knight and I brought him down to our level. It wasn't hard. You see, madness, as you know, is like gravity. All it takes is a little push."