'The Blind Side': Making This Season's Surprise Box Office Smash Hit

Dec. 24, 2009— -- Hollywood loves a success story -- and they have it with "The Blind Side," the tale of football player Michael Oher's path from poverty and homelessness to NFL stardom.

The movie "The Blind Side" has become the season's surprise hit, raking in more than $150 million at the box office and earning a Golden Globe nomination -- and Oscar buzz -- for its star, Sandra Bullock.

Director John Lee Hancock told "20/20" he had only read a few chapters of Michael Lewis's book "The Blind Side" when he decided that he wanted to write and direct the movie.

"This was really a terrific story, and it was kind of more of an unconventional mother/son story than it was a sports movie. So about fifty pages in, I was in," he said.

Hancock said he also knew that Sandra Bullock would be the ideal actress to play Oher's adoptive mother Leigh Ann Tuohy.

Watch "The Blind Side: The True Story Behind the Movie" on a special edition of "20/20," Tuesday, Dec. 29, at 10 p.m. ET

"Everybody knows her for her comedy skills and her behavior comedy, and her sharp tongue, and those are formidable skills, but I didn't think that she'd been given the chance to...show off the really great dramatic talent that she has," Hancock said. "I knew that she could pull it off."

Next, the director said he had to find an actor to play her husband, Sean Tuohy.

"I cast Sandy and started thinking about it, I sort of, I realized that there would be a lot of actors that would become wallpaper quickly," Hancock told "20/20." "I needed someone that was comfortable in his own skin, and had the kind of a self-effacing sense of humor."

Country music star Tim McGraw came on board despite initial reluctance to appear in a sports or family movie after his roles in "The Rookie" and "Flicka."

"I read it and just fell in love with the ...characters and the people," McGraw said, "And I gave it to my wife to read, and she loved it as much as I did. It's just rare that you come across a story...that moves you that much."

Click here to see Tim McGraw talk about his 'Blind Side' role.

For Hancock, it turned out that enlisting A-list stars was the easy part. He said the real challenge came when it was time to cast an actor to play Michael Oher -- the "gentle giant" on whom the film centered.