Alyson Hannigan is set to play Sally to Luke Perry's Harry. The actress has just been cast in the London stage version of Rob Reiner's 1989 film "When Harry Met Sally," playing the part originally made famous by Meg Ryan. Directed by Loveday Ingram, the production is set to unveil in previews Feb. 10 with an official opening Feb. 20 at the Theatre Royal in London. Produced by James Tod, "When Harry Met Sally" is scheduled to run for 16 weeks. Marcy Kahan adapted Nora Ephron's script for the stage. It will find Hannigan and Perry as longtime friends who keep bumping into each other through the years while they separately search for love, always afraid to hook up with each other for fear that sex will ruin their good friendship. Hannigan is repped by Innovative Artists and manager Steve Lovett and Lovett Management. She is best known for her work as Willow on "Buffy the Vampire Slayer" as well as her part in the "American Pie" franchise as the flute-toting love interest of Jason Biggs' character.