That’s the way I describe Joss Whedon’s latest mini-masterpiece, Dr. Horrible’s Sing-Along Blog.

I became a Joss Whedon fan when I saw Firefly. I only started watching his earlier cult hit Buffy the Vampire Slayer a few days ago, so I’m late to that one.

Dr. Horrible’s Sing-Along Blog is a three-part mini musical that was written during the writer’s strike by Joss, his brothers Zack and Jed, and Jed’s fiance Maurissa Tancharoen. The show was viewable for free during the week of July 15 through July 20th (last week as I write this). Sadly, it is currently only available through iTunes, but the $3.99 you have to cough up to own all three parts of this 40-minute musical is well worth it.

The musical stars Neil Patrick Harris (Doogie Howser, M.D.) as Dr. Horrible (real name: Billy), an evil villain whose master plan is to perform an act of evil and thus gain entry into a nefarious society known as the Evil League of Evil, and eventually rule the world.

Dr. Horrible’s nemesis is the super hero Captain Hammer, played by former Firefly star Nathan “I’m heterosexual but even I’ll admit he’s a hottie” Fillian. Captain Hammer has constantly thwarted Dr. Evil’s plans of world domination.

To say much more about the plot — especially the more pedestrian, non-super-hero parts — would ruin the fun. Suffice it to say that the third main character in the show is Penny, played by Felicia Day; she forms the third point in a sordid, musical love triangle, and that is where the fun of this musical really lies.

It’s a comedy, but it’s not without its tragedy and not-so-subtle social commentary. But above all, it’s fun and funny.

Nathan Fillian really hams it up as Captain Hammer, and Neil Patrick Harris delivers a great performance as an evil genius that you almost want to sympathize with.

Musically, the show is incredibly complex. Each of the three main characters has a “theme melody” that they he/she carries through the film. But what’s great is that, like many classic musicals like The Music Man, these three disparate themes elegantly criss-cross, overlap and intertwine in some of the show’s best songs, making for some great ensemble pieces.

Although the show is only viewable on iTunes, it will soon be coming to DVD (with plenty of extras, including, as mentioned by Joss, a DVD musical commentary!) soon along with the soundtrack.

The show has proven to be more popular online than anyone had anticipated, even causing a server crash when, according to the web guys at video-streaming service Hulu.com, 1000 people tried to watch the show in the same instant.

Joss Whedon was recently quoted in an L.A. Times article as saying that he and his fellow Dr. Horrible writers are currently “too busy talking about the giant Broadway adaptation, the much longer film version and the musical commentary that we’re writing now.” This quote almost screams tongue-in-cheek, but I guess time will tell.

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