The latest in a family of celluloid sex symbols, Dakota Johnson is the spitting image of her grandmother Tippi Hedren (famously terrorized in Hitchcock's The Birds), with the come-hither eyes of her mom, Melanie Griffith. Having also inherited the L.A. cool of dad Don Johnson, the 22-year-old former IMG model has rolled with gossip-page staples (Riley Keough, Rumer Willis). Recently, however, she's been trying to keep pace with Hollywood's reigning kings of comedy, starring opposite Jonah Hill in 21 Jump Street and playing Jason Segel's temptress in next month's The Five-Year Engagement. "I've never had training in improv, and it's all improv," Johnson says. "It's like, 'Okay, you guys are the best—and I've never done this.' It was terrifying." But don't let the wallflower act fool you. In 2010's The Social Network, wearing just a sweatshirt and strategically cut underwear, she was the picture of hot collegiate confidence as Justin Timberlake's one-night stand. Growing up, "it was such a task to put clothes on, and when I did I'd look like a crazy person," Johnson says. "My parents would be like, 'Dakota, you don't have to wear tights and jeans and a skirt.' Being naked was just more comfortable." Does she still feel that way? "Well, yeah."