Dr. Horrible's Sing-Along Blog is a musical comedy by Joss Whedon (Buffy, Firefly), featuring the wannabe mad scientist Dr. Horrible bent on taking over the world (played by Neil Patrick Harris). There is also Penny (Felicia Day), the cute girl he really likes, and Captain Hammer (Nathan Fillion) who keeps beating him up. It will be streamed for free on the show's official website in three chapters (each about 14 minutes). It is the first of its kind, and it's going to be awesome - don't miss it!