Mutant Enemy was Joss Whedon's production company, and its logo closed episodes of Buffy the Vampire Slayer from 1997 to 2003, as well as Angel and Firefly. A simple paper-cutout style monster walked across a white background while Whedon himself voiced the grr argh line. Because it appeared after dramatic episode endings, fans came to read it as a comic release and an in-joke. The tag was later varied for special episodes, which helped keep the little growl in fan culture long after the shows ended.