Alyson Hannigan.

Alyson Hannigan (born Allison Lee Hannigan March 24, 1974) is an American actress best known for playing Willow Rosenberg in the TV series Buffy the Vampire Slayer. She also appeared in films including, as Michelle Flaherty, American Pie (1999), American Pie 2 (2001) and American Wedding (2003).

Born in Washington, DC to an Irish-American father and a Jewish-American mother, her first film role was in My Stepmother is an Alien (1988).Before that she had done a little television work, mostly commercials, and she went on to do a good deal more including Almost Home, Picket Fences, Roseanne and Touched by an Angel before being chosen for Buffy in 1997. By the final season she was earning $250,000 an episode.

It was announced in October 2003 that she had signed a deal with NBC to appear in a comedy, expected to debut in fall 2004. Reports indicated that it was likely to be titled Americana, but the pilot was not part of NBC's 2004 fall lineup.

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.

She owns a home in Sacramento, California and married actor Alexis Denisof (who played Wesley Wyndam-Pryce in the Buffy franchise) on October 11, 2003. Previous relationships include actor Steven Sutphen and Marilyn Manson drummer Ginger Fish.

In 2005, Hannigan is one of several Buffy cast returning to television - others being David Boreanaz, Nicholas Brendon, Charisma Carpenter and James Marsters - as part of the cast of the new TV series "How I Met Your Mother", as well as a recurring guest role on Veronica Mars.

Hannigan's somewhat unstereotypical looks and specific acting style have led her to, for the most part, choose somewhat quirky characters (her best known roles in BtVS and the American Pie series being clear examples of this), which more appropriately fit her.