An actor since childhood, Alyson Hannigan is known to TV viewers as Willow Rosenberg, one of the monster-fighting sidekicks from the series Buffy the Vampire Slayer (1997-2003, starring Sarah Michelle Gellar). Hannigan got her start at an early age, working on TV commercials in Atlanta, Georgia. When she was 11 she relocated to Los Angeles and found work guest-starring in several television comedies before landing the role of Willow.
Hannigan has appeared in feature films also, most notably American Pie (1999), American Pie 2 (2001) and American Wedding (2003). She returned to television in the series, How I Met Your Mother in 2005, and had a recurring guest role on the teen drama Veronica Mars in 2006.
Hannigan has appeared in feature films also, most notably American Pie (1999), American Pie 2 (2001) and American Wedding (2003). She returned to television in the series, How I Met Your Mother in 2005, and had a recurring guest role on the teen drama Veronica Mars in 2006. 
In 2003 Hannigan married actor Alexis Denisof, a co-star of Buffy and its spin-off series, Angel.