I don't know that I can explain this fully here, but let me sum up: Joss Whedon (Buffy) and friends got together during the writers strike and this is what they came up with. It's an internet-distributed show in three acts of around 15 minutes each. It's a musical. It stars Neil Patrick Harris as Dr. Horrible, a would-be mega villian with a crush on a lovely ingenue. Don't miss Nathan Fillion as Captain Hammer, a superhero, and Dr. Horrible's nemesis.