This appealing actress specializes in playing awkward, nebbishy characters who somehow manage to possess a come-hither allure. A former child model who landed her first job in an instructional film at the age of 3 months, Hannigan moved from Atlanta to Los Angeles and segued to acting while in her teens. After a number of stints on such series as Free Spirit, Roseanne and Touched by an Angel, she came to prominence in 1997 on Joss Whedon's inventive fantasy-dramedy series Buffy the Vampire Slayer, portraying nerdy witch Willow Rosenberg and adding a charming, oddball element to the character for six seasons. (She also played the character in a recurring turn on Angel, a Buffy spin-off.) Both her acting and love life blossomed while on Buffy, as she ended up marrying costar Alexis Denisof. She then scored a plum part in the big-screen American Pie trilogy as high-school flutist Michelle Flaherty, whose band-geek exterior belied an overly naughty persona. After making her stage debut in 2004 in a London production of When Harry Met Sally, she returned to her small-screen roots in 2005 to star on the sitcom How I Met Your Mother. She indeed became a mother in 2009, giving birth to a baby girl, Satyana Denisof.