This is the mascot of Mutant Enemy, the production company of Joss Whedon, seen at the end of such classic shows as Firefly, Angel, and Buffy the Vampire Slayer. He stalked across the screen with his trademark phrase, "Grr! Arg!", letting us know that another great episode had come to an end. How many people out there can say these two words to a friend and have them dissolve into giggles? I'm raising my hand!