Mutant Enemy Productions was the production company created in 1997 by Joss Whedon to produce Buffy the Vampire Slayer. The company also produced the television shows Angel, a Buffy spin-off; and Firefly, a short-lived space Western.
Its offices (made out of glass bricks) were on the lot of 20th Century Fox in Los Angeles, previously the home of Chris Carter's Ten Thirteen Productions. According to March 2006's issue of UK magazine The Word, the office (and thus the company) were closed not long after Angel was cancelled (though a date was not given). The film Serenity credits Barry Mendel Productions instead.
The name "Mutant Enemy" is taken from the song "And You and I" by prog rock band Yes, of whom Whedon is a confessed fan. It was also the name Whedon had given his first typewriter.