With her chestnut mane, crystal-blue eyes, and pleasing proportions, Alison Brie would have no trouble finding work even if she couldn't act. But her mastery of both nuanced drama and fast-paced comedy—on two of TV's most talked-about shows, no less—makes her even hotter: On AMC's Mad Men, back for its fifth season, she's riveting as the petulant, baby-obsessed sixties housewife Trudy Campbell; on NBC's Community, soon to resume its third season, she's irresistible as Annie, a good girl with a complicated backstory (which includes an Adderall addiction and a nervous breakdown) who could go bad at any moment. That combination of primness and wildness has turned her into fantasy fodder for fans: "My parents Google me enough to let me know when there's fake Facebook pages of me," Brie says. "My mom and sister will call and say, 'Oh, there's a you on Facebook again—and they posted some racy photos."

In this month's Judd Apatow-produced The Five-Year Engagement, the classically trained 29-year-old actress showcases her comedic chops in a scene-stealing turn as Emily Blunt's kooky little sister. She won the role, she says, thanks to an uncanny ability to imitate Sesame Street's Elmo; in one scene, her character adopts the puppet's high-pitched squawk to offer advice about whether to tie the knot: "Elmo thinks you should shit or get off the pot!"

The Southern California native also pulls off a highly credible British accent. "Emily would lean over every once in a while and be like, 'Don't forget: toh-mah-toe,'" Brie says. "I remember us getting really caught up on 'lit-ruh-lee': 'I lit-ruh-lee cahn't believe that! I lit-ruh-lee hate you right now!'" What makes her bits—from a drunken engagement-party toast to a rendition of a schmaltzy Portuguese pop song—so funny is that she delivers them with the kind of steely confidence that even Don Draper would appreciate. "A lot of comedy is about just kind of going for it," Brie explains. "I have this ability to think I'm hilarious all the time."

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