Alyson Lee Hannigan (born March 24, 1974) is an American actress. She is known for her roles as Willow Rosenberg in the television series Buffy the Vampire Slayer, Lily Aldrin on the CBS sitcom How I Met Your Mother, and Michelle Flaherty in the four main original American Pie film series.
Hannigan was born in Washington, D.C. She is the only child of Emilie (Posner) Haas, a real estate agent, and Al Hannigan, a truck driver. Her father is of Irish descent and her mother is Jewish. Her parents divorced when she was two and she was raised mostly by her mother in Atlanta, Georgia.
At age four, Hannigan began appearing in commercials. She moved to Hollywood at age 11. Living with her mother and attending North Hollywood High School, she successfully auditioned for agents while visiting her father in Santa Barbara. After attending North Hollywood High School, she attended California State University, Northridge where she earned a degree in psychology.
Hannigan's first major film role was in My Stepmother Is an Alien, a science fiction comedy released in 1988; one of her co-stars in the film was actor Seth Green, who would later join her in the regular cast of Buffy as her on-screen boyfriend . Then in 1989, her first regular role on a TV series came when she was cast in the short-lived ABC sitcom Free Spirit.
As a teenager, Hannigan babysat for Bob Saget, who would later narrate her TV series, How I Met Your Mother.
In 1997, Hannigan was cast to play Willow Rosenberg , Buffy's best friend, on the television series Buffy the Vampire Slayer . The show became a success, and Hannigan gained recognition, subsequently appearing in several notable films aimed at teenage audiences, including American Pie, American Pie 2, Boys and Girls and American Wedding. By the time Buffy ended in 2003, Hannigan was earning a US$250,000 salary for each episode. She also had a guest spot on the Buffy spin-off, Angel , reprising her role of Willow in a few episodes (including most notably "Orpheus," during the fourth season of Angel and the seventh season of Buffy), but none after Buffy finished production.
In early 2004, Hannigan made her West End debut, starring in a stage adaptation of When Harry Met Sally... at the Theatre Royal Haymarket, opposite Luke Perry.
In 2005, Hannigan returned to starring in a regular television series, appearing in the hit comedy, How I Met Your Mother, as Lily, and also playing a recurring guest role on Veronica Mars as Trina Echolls.
In February 2006, Hannigan starred as Julia Jones in Date Movie, a parody of romantic comedies. She was also a guest star on the ABC animated sitcom The Goode Family in 2009.
Hannigan joined forces with Emily Deschanel, Jaime King, Minka Kelly, and Katharine McPhee in a "video slumber party" featured on FunnyorDie.com to promote regular breast cancer screenings for the organization Stand Up 2 Cancer.
In 2012, Hannigan reprised the role of Michelle in American Reunion.
Alyson Hannigan later guest-stared, with Joss Whedon, Charisma Carpenter (Cordelia Chase), Christian Clemenson (Balthazar), Adam Kaufman (Parker Abrams), Jesse James (Ryan Anderson), Steve Rankin (Mr. Maclay), Deborah Zoe (Mistress Meerna), Brittany Ishibashi (Vivian) and Megalyn Echikunwoke (Vaughne) on Veronica Mars.
Alyson Hannigan later starred one of the principal roles on How I Met Your Mother. This show include also many guest-stars of Buffyverse like Seth Green (Oz), Danny Strong (Jonathan Levinson), Carlease Burke (Winslow), Danielle Weeks (Debbie Foley), Phil Lewis (Stephen Platt), Harry Groener (Richard Wilkins), Alexis Denisof (Wesley Wyndam-Pryce), Michele Nordin (Rachel), Kal Penn (Hunt/Brain man), Greg Collins (Keith), Chris Tallman (Nick Straley), P.J. Marino (Peter Wilkers), Rebecca Klinger (Madame Dorion), Todd Stashwick (Vocah/M'Fashnik Demon), Tom Lenk (Cyrus/Andrew Wells), Stewart Skelton (Harold Jeakins), Ezra Buzzington (Unidentified Bartender (Willy's Bar)), Amy Acker (Winifred Burkle/Illyria), Mike Grief (Klyed), Sam Littlefield (Bobby), Ken Takemoto (Chinese demon man), Pat Crawford Brown (Wig Lady), Eric Bruskotter (Brian), Kevin Christy (Josh), Thomas Crawford (Eater Demon), Caroline Lagerfelt (Anne Pratt), Peter Breitmayer (Desmond Keel) and Nick Jaine (Sahrvin Clan leader).
Hannigan married actor Alexis Denisof at Two Bunch Palms Resort in Desert Hot Springs, California, on October 11, 2003. The couple have two daughters, Satyana Marie Denisof, born March 24, 2009, and Keeva Jane Denisof, born May 23, 2012.
Alyson Hannigan is one of the only two characters to appear in every 144 episodes of Buffy the Vampire Slayer along with Buffy Summers herself Sarah Michelle Gellar.
She appeared on How I Met Your Mother as Lilly Aldrin, she is a regular.
She portrayed the initially shy, but later powerful and assertive witch Willow Rosenberg. Willow later on determined her identity, crucially realizing she was homosexual. She had an alternative vampire character, Willow Rosenberg (Wishverse), who was her opposite, being a sexy dresser, a bad-ass and obviously a vampire.