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Despite her fears, the critically acclaimed writer and actress says she already has the support of the HIMYM cast. "They're so nice! I went and I hung out with all the cast and they were like, 'If you can be part of this world, it's crazy fun,'" she gushed. "They told me they believed in me, and it was really sweet." Well, if she's got Lily's (Alyson Hannigan) approval, then you know she must be the perfect fit!

The Frances Ha actress will take on the role of Sally, a sweet yet free-spirited girl in her late-20s who has never really embraced the notion of growing up. However, unlike Ted (Josh Radnor), Sally is already married when we first meet her in the pilot.

In addition to starring in the series, Gerwig will also be taking on a major behind-the-scenes role as a writer and executive producer alongside co-creators Carter Bays and Craig Thomas. "I contributed a lot into the pilot, and I'll be in the writers room staring June 1 if they pick it up," she said. "I shoot the pilot in like two weeks and then hopefully it becomes a real show."