The production company that made Firefly, Buffy the Vampire Slayer, Angel, Doctor Horribles Sing Along Blog, and Dollhouse. All about Joss Whedon. Origin: "Mutant Enemy" was the nickname Joss Whedon gave to the typewriter upon which he started his writing career, and came from the Yes song "And You And I" (specifically, the third section of the song entitled "The Teacher and the Preacher"), a band Whedon is a big fan of. This song was inspired by Isaac Asimov's "Foundation" series of books, and the "mutant enemy" of that series was a character called the Mule.