Act 2 of Joss "Firefly" Whedon's online supervillain musical Dr. Horrible's Sing-Along Blog arrived on the innerwebs yesterday, and it was a great moment in evil. We get a lot more mugging from Captain Hammer (Nathan Fillion), as he begins dating Penny, the love of Dr. Horrible's life. In this clip, Hammer drops by the laundromat where Horrible and Penny hang out — and engages in some pretty awesome smack-talking. Including possibly the best penis joke ever.

This scene leads into what is probably the most metal-esque moment in the show so far, with Dr. Horrible singing about how he's totally certain he's going to become an evil killer now that Hammer has taunted him to the point of mania. Plus, he has Bad Horse to please — the leader of the Evil League of Evil wants Horrible to prove himself to gain entrance to the League.

As ever, the show centers on Dr. Horrible's videoblog, which he has now discovered is so popular that the police watch it, as well as Captain Hammer. Which makes it hard for him to pull of heists he's talked about a lot in the previous entry. (The Freeze Ray didn't work out so well, because Hammer was waiting for him at the "secret demo" and threw a car at his head.

So far Dr. Horrible's Sing-Along Blog has succeeded in toying with the online medium in a way that few online serials have save for perhaps Homestar Runner. Homestar's Strong Bad Email segments always remind you that what you're watching is on the internet rather than TV. This is sort of the opposite approach of most online video, which generally tries to be as close to TV as possible. This show is unapologetically a blog, however, and it's exciting to see television creators paying tribute to a web medium for once, rather than the other way around.

If online video is ever going to become a medium that challenges network TV, that challenge is going to start with shows like Dr. Horrible. Shows that aren't afraid to be what they are. You know, blogs. Where people sing and wear rubber gloves and take over the world.

Watch the new segment free here or buy it on iTunes. Get ready! The final episode airs Saturday, and then Sunday at midnight it will no longer be available until the DVD arrives.