Fallon wasn't too shabby himself, performing admirable renditions of Iggy Azalea's "Fancy" and Styx's "Mr. Roboto."
late 14c., the Greek river of the Underworld, cognate with Greek stygos "hatred," stygnos "gloomy." Oaths sworn by it were supremely binding and even the gods feared to break them. The adjective is Stygian.