Born On: 24 March 1974 Place of Birth: Washington, District of Columbia, USA Birth Name: Allison Lee Hannigan Also Known As: Allycat Height: 5' 6" (1.68 m)   Alyson Hannigan is an American actress who plays Lily Aldrin in the CBS sitcom How I Met Your Mother.

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. Throughout most of the early 1990s, she appeared in commercials and supporting roles on television shows, including Picket Fences, Roseanne and Touched by an Angel.

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 big 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.

She married actor Alexis Denisof (who played Wesley Wyndam-Pryce in the Buffy/Angel franchise) in Los Angeles on October 11, 2003. They bought a home together in Santa Monica, California.