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.
- At the age of 3 months, appeared in the industrial film Active Parenting.
- Was a child model, beginning at the age of 4 and appearing in more than 100 print ads and 30 TV commercials before she was 11.
- Breakthrough role came in 1988, playing Dan Aykroyd's daughter in the movie My Stepmother Is an Alien.
- Received the Golden Satellite award for Best Ensemble Television Cast in 2001 for Buffy the Vampire Slayer.
- In 2004, made her stage debut in a London production of When Harry Met Sally.
- Shares a birthday (March 24) with her elder daughter, Satyana.
- 2010, People's Choice Awards — Favorite TV Comedy Actress: Winner
- Albert Hannigan — Father
- Emilie Posner — Mother
- Ginger Fish — Ex-significant Other
- Alexis Denisof — Husband
- Keeva Jane Denisof — Daughter
- Satyana Denisof — Daughter
- Attended California State University, Northridge, California, United States
- Birth Name: Allison Lee Hannigan
- Birth Place: Washington, District of Columbia, United States
- Profession: Actor, Model