Dr. Blog-Bot of DoctorHorrible.net, a fan site dedicated to Dr. Horrible's Sing-Along Blog says that Joss Whedon has promised very special DVD extras including a "musical commentary."
"Dr. Blog-Bot of DoctorHorrible.net, a fan site dedicated to Dr. Horrible's Sing-Along Blog discusses how fans reacted to issues during the Joss Whedon web series debut and how the faithful have taken to it since."