
Lets get to the facts on the film.
"Welcome to a world without rules."
Director : Christopher Nolan
Writers : Johathan Nolan, Christopher Nolan, David S. Goyer
Who is Christopher Nolan?
Born in England Chris began making films at the age of seven using his dad camera. He graduated to making films involving real people. Other films in which he was involved are Batman Begins (2005), Memento (2000) and Doodlebug (1997)
Who is Johnathan Nolan?
Born in London and attended Lyola Academy in Wilmette where he graduated in 1994. Apart from The Dark Knight he was also involved in Memento (2000), The Prestige (2006) and is in post production in Terminator Salvation.
So what actors did the writers want, to make their story to come to life?
( below a few character profiles i made with basic information)

Actor : Heath Ledger
Character : The Joker
Outline of Character: The Joker is not insane - he is just too clever for his own good. He gets bored so easily, and therefore makes a sport out of duelling with Batman.

Actor: Christian Bale
Character : Bruce Wayne/ Batman
Character Outline: Batman, Gordon and Harvey Dent are forced to deal with the chaos unleashed by an anarchist mastermind known only as the Joker, as it drives each of them to their limits

Actor : Maggie Gyllenhaal
Character : Racheal Dawes
Character outline: In "The Dark Knight", she is now working for DA Harvey Dent. She is a relationship with Dent as well, much to Bruce's dismay. She is eventually tied up in a warehouse full of explosive oil and is killed in an explosion.

Actor : Micheal Caine
Character: Alfred Pennyworth
Character outline: Alfred Pennyworth is the faithful butler to multi-billionaire Bruce Wayne aka The Batman

Actor: Aaron Eckhart
Character: Harvey Dent/ Two-Face
Character outine: Once a high-profile District Attorney for Gotham City, Harvey Dent was horribly disfigured by an attack

Actor : Morgan Freeman
Character : Lucius Fox
Character outline: The man who essentially runs Wayne Enterprises for his employer Bruce Wayne
Actor: Gary Oldman
Character : James Gordan
Character outline: James Gordon is a police lieutenant in the Gotham City Police Department. He has become a friend and ally to the Batman.
Warner Bros...
...is the largest producers of film and entertainment. It was founded in 1918 by Jewish immigrant from Polond. It is the third oldest American movie studio.
Legendary Pictures

Is one of the companies to help produce The Dark Knight. Legendary Pictures is an American motion picture production company based in california. The company is in agreement with to co-produce and co-finace with Warner Bros. Their first full length feature film with Warner Bros was the comic book movie Batman begins, so they have know how in batman film and the comic style to help with The Dark Knight.