For a 42-minute film, the DVD release of Dr. Horrible's Sing-Along Blog has a nice amount of extras. There are not one but two commentaries! The first commentary is a standard one with actors Nate Fillion, Neil Patrick Harris, Felicia Day, and Whedon, where the participants have fun talking about the shoot for the film, flubs, all the fun they had, and more. Then there’s “Commentary! The Musical” — this is a musical commentary track that the cast and crew perform that’s made up of entirely new numbers created just for the DVD release.
“ELE (Evil League of Evil) Applications”. At the 2008 San Diego Comic-Con Dr Horrible panel it was announced that the producers would accept short films from the fans about why their character should be inducted into the ELE. They took the ten best and included them on the DVD. Some are truly hilarious and you can see who really liked Dr. Horrible's Sing-Along Blog.
There are also several making-of featurettes which go behind the scenes of this film that are both fun and informative. Whedon has plans for a sequel but is keeping quiet as to whether it will be another Internet movie, or maybe a big screen adventure. Either way fans are eager for the next installment of Dr Horrible and it can’t get here soon enough!