
No one knows this. But, yes, it was on TV. It even won a prime time Emmy (Outstanding Special Class - Short-Format Live-Action Entertainment Programs).
Everyone who's already seen this thinks it went straight to the Internet. Where it gained so much fame (Joss Whedon fans are devoted!) that you can no longer view it at its website. It is, however, available on Netflix (streaming!) or to buy via Amazon.com and other places, I'm sure.
As eluded to, Joss Whedon (creator of Buffy, Angel, Firefly) and his brothers Jeb and Zack wrote this... I'll just call it a Short (42 min total). It stars Neil Patrick Harris (Doogie Howser, MD.) as Billy who is trying to cement his role as Dr. Horrible, evil genius/super villain, and impress his wanna-be girlfriend, Penny. Standing in his way is Captain Hammer, played by Nathan Fillian (Firefly, Castle).
The Whedon brothers are very crafty mixing live action with Dr. Horrible's blog (actually a podcast), and the musical numbers fit in perfectly. Most of the songs are really good, too. Maybe not Roger's & Hammerstein, but they are surprisingly complex (in places), catchy, witty, drive the story...you know, good. But the biggest surprise: Doogie Howser can sing!!
The writing is spectacular. Very few could execute so well the idea of someone trying to become a member of the "Evil League of Evil", and still make the character sympathetic and real.
I found this an absolute joy to watch. But I should point out that this is not all flowers and wine - after all the main character is an anti-hero.