Known for her wit, charm and approachable beauty, this first-time Oscar nominee became famous for acting in films such as "Speed," "While You Were Sleeping," "Miss Congeniality" and "The Proposal." Playing a real-life Tennessee mom who took in a homeless teenager proved that Bullock had serious acting chops and the talent to match.
But before Bullock was America's sweetheart, she was Arlington, Va.'s funny girl. ABC News sat down with one of her classmates at Washington Lee High School to get the dirt on what she was like before she was famous.
"She was the class clown, the funniest girl at Washington Lee," said Bullock's former classmate and friend, Scott Sowers. "She was into as much as you could possibly do."
Watch "Before They Were Famous," on a special edition of "20/20" Tuesday, March 2 at 10 p.m. ET
Sowers recalled that Bullock was a varsity cheerleader, spoke fluent German, participated in the ski club and was a member of the thespian honor society.
Even at an early age, Bullock was a ham. Home video obtained by ABC News and shot by Arthur Bloch, a man who drove Washington Lee High School students to sporting events and became their unofficial photographer, shows Bullock parading in front of the cameras at a game, showing off her cheers, wearing braided pigtails.
Always the jokester, Bullock once decided to dress up as a mouse for a cheerleading yearbook photo. Sowers recalled an incident where her playfulness got her in trouble.
"We'd been goofing around, and laughing too much, and we were scolded and told to calm down," recalled Sowers. "And so naturally that's our cue to clown around more. And she's always been an easy target to get to laugh."
According to Sowers, their drama teacher once turned to Bullock and said, "when you get a C in this class, don't ask me why. And I'll tell you something, if you don't start taking this seriously, you're never going to make it."
Somewhere along the line, Bullock apparently got serious. She told her mother she wanted to pursue acting as a career.
Bullock asked Sowers to come with her when her portfolio pictures were taken, and together the friends posed in cowboy hats and rain gear -- pictures Sowers shared with ABC News.
"She's got a raincoat on, pretending to flash me," Sowers said. "We just clowned around for about two hours."
Bullock became more serious about acting later in high school. She won an award for best actress in a talent competition for her performance in "A Streetcar Named Desire." She also starred in Woody Allen's "Don't Drink the Water," and was always putting on performances in school assemblies. Bullock wrote a lot of sketches with Sowers and was eager to perform them whenever an opportunity presented itself.
For a high school talent show one year, Bullock announced she wanted to do something creative in between the skits.
"I would come out to introduce the next act and then she would come on in a character and start tap dancing," said Sowers. "Or she'd come out and start juggling or she'd come out and start singing...and she stole the show."