Shoshanna, the character Zosia Mamet plays on HBO's new Lena Dunham-helmed, Judd Apatow-produced comedy Girls, is the type of young woman who proudly displays her Sex and the City poster in her bedroom, and wears light pink velour jumpsuits. "She is literally the opposite of me," Mamet says. That is to say, a virginal, "Jewish American Princess with an unexpected inner life," as the show's creator, director and star Dunham-- she of 2010's breakout, low-budget film Tiny Furniture--recently tweeted. And while Shoshanna is one of the show's four early- 20-something leading ladies living and wondering what they're doing with their lives in Brooklyn, Mamet knew what she wanted to do with her life "from day one."

Her father is legendary playwright and director David Mamet, her mother actress Lindsay Crouse. "My mother was on stage when she was pregnant with me, I think I was a goner from the get-go." Mamet was never particularly interested in school ("every year I was in high school I tried to drop out") so after graduation, she decided not to go to college, and got straight to work with a recurring role on United States of Tara and standout parts as Peggy's lesbian friend in Mad Men, and a hyper-sexualized teen in The Kids Are All Right. Mamet's recently been cast in Shoplifters of the World (a comedy that takes place the night The Smiths broke up), and is keeping her fingers crossed that Girls, which premieres this month, gets renewed for a second season. "It's really the calm before the storm," she says, "even though we're not exactly sure what the storm is going to be."

 Zosia wears a bra by Mariah Serrano.