When he's not busy breaking the law or trying to get close to his secret crush, Penny (Felicia Day), supervillain wannabe Dr. Horrible (Neil Patrick Harris) boasts about his exploits via his Internet video blog and dreams of defeating his nemesis, Captain Hammer (Nathan Fillion). Conceived during the 2008 Hollywood writers' strike, Joss Whedon's quirky musical comedy originally debuted as an online miniseries.