What is 'The Social Network'? Who is 'The Social Network'? ET breaks down the Facebook movie that everyone's talking about…

In 'The Social Network,' the film inspired by the true story of the creation of Facebook, 'Zombieland' star Jesse Eisenberg plays Mark Zuckerberg, the genius Harvard student with a vision that ultimately became the website with approximately 500 million members.

"People want to go on the Internet and check out their friends, so why not build a website that offers that?" says Jesse as Zuckerberg in the movie.

Justin Timberlake plays the wild card, Sean Parker. The entrepreneur that founded Napster was highly influential in the success of Facebook and became its president in 2004 when the company incorporated.

"I don't feel a responsibility to mimic anyone who's living," says Justin about playing a real-life person. "I feel a responsibility to create a character that's interesting for the film, and I feel that's what we're all doing."

"Justin, when I heard that he was going to play that part, I thought it was such a great choice, and selfishly so, because my character sees him as like a rock star," says Jesse.

Andrew Garfield, recently tapped to play the new 'Spider-Man' and also seen this fall opposite Keira Knightley in 'Never Let Me Go,' plays Zuckerberg's best friend, Eduardo Saverin, who was with Facebook from the very beginning, and reportedly later sued the company for a massive sum, eventually settling the case.

"My relationship with [Jesse] is my linchpin, that's all I kind of have to anchor me to the circumstances, and if he didn't feel like a brother to me, then it wouldn't work," says Andrew.

In theaters October 1, 'The Social Network' is directed by David Fincher ('The Curious Case of Benjamin Button,' 'Zodiac,' 'Fight Club') and follows the incredible true story of Zuckerberg's transformation from an undergrad student and computer genius to the world's youngest billionaire - and the enemies he made along the way.

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Like! An Exclusive Preview of 'The Social Network' Sep 20, 2010 12:07 PM