Alyson Hannigan has been acting for basically her entire life, having started appearing in commercials at the age of four. Her first major film role came ten years later in the 1988 comedy My Stepmother is an Alien, alongside her future Buffy the Vampire Slayer co-star Seth Green. Throughout the late 80s and the 90s, Hannigan worked primarily in television, appearing on shows such as Roseanne and Touched by an Angel. Her big break came on the 1997 Joss Whedon series Buffy the Vampire Slayer, and she had a smash hit with the film American Pie a couple of years later. Since then, Hannigan has appeared in the American Pie sequels American Pie 2, American Wedding and American Reunion, and on TV series such as Angel, That 70’s Show, Veronica Mars, King of the Hill, American Dad, and How I Met Your Mother. Alyson Hannigan turns 39 today.