This is the greatest thing ever. Ever. Go. Now. Watch.
Update 7/21: Shame on anyone that missed the free viewing of Dr. Horrible’s Sing-Along Blog, which ended today. Extra shame on anyone that still has no idea what Dr. Horrible even is. What’s not to love about a fourty-minute web musical starring a low-rent supervillain trying to make it into the Evil League of Evil and win the girl of his dreams whom he sees every weekend at the laundromat (who’s inadvertently swept off her feet by his arch-nemesis Captain Hammer)?
Everyone involved is spectacular, but I was particularly amused to see Nathan Fillion playing the moronic Captain Hammer. I just about died during “Everyone’s A Hero” when he started singing about “bashing in minds.” 
There are even a couple of twists n the final act that caught me off guard. One isn’t too difficult to guess at, but the other was pretty shocking and very sad.
If you are one of the unfortunate souls that completely missed out on the free viewing you can still pick it up on iTunes. $3.99 for the entire series is a steal, and a soundtrack is supposed to be out soon. Do yourself a favor and buy it.