Message from the band itself:
While the live-action Decemberists are still hibernating, their animated counterparts are poised to debut on The Simpsons Sunday night (December 9) at 8pm ET on FOX (and live on into eternity through the power of syndication). Their appearance isn't a mere cameo - the band also wrote and recorded original music for the episode. And Colin penned his line himself which makes it that much more Decemberist-ier.
The episode, entitled "The Day The Earth Stood Cool," also features the great Patton Oswalt, Carrie Brownstein and Fred Armisen. Be sure to tune in via your preferred visual entertainment medium