Kathryn Felicia Day, known generally by her middle name, is an American actress who plays Holly Marten on Eureka. Her role frequently references her popularity with the Internet community as the writer/creator/star of "The Guild". Her other roles include the Joss Whedon online project Dr. Horrible's Sing-Along Blog as Neil Patrick Harris' love interest. She also plays the role of Charlie Bradbury in "Supernatural".