During the writer strike, Joss Whedon teamed with his brothers to bring us Dr. Horrible’s Sing Along Blog in what was a web-only format. The three episodes could have been purchased through iTunes at the time, but after that first week of availability, they disappeared. Now, Amazon.com has an exclusive on the production through their DVD-R media, due December 19, which can be preordered here. Why DVD-R? I haven’t tracked down a press release, but I suspect it’ll be a limited time offer once more, and the DVD-R option avoids overstocking on unsold copies.