Two unlikely foes have launched a mock feud to be fought in a sea of green.

Stephen Colbert of Comedy Central’s “The Colbert Report,” earlier this year held a “Green Screen Challenge,” in which he implored fans to fill in the green background of a video of Colbert skewering an imaginary enemy with a lightsaber.

His loyal Colbert Nation (and George Lucas) responded with a number of creative, animated scenarios (http://colboard.com/cn/greenscreen.php).

The Decemberists, the critically acclaimed indie rock group fronted by Colin Meloy, recently announced a competition of their own. Their mtvU-sponsored “Reanimated the Decemberists” offered fans a chance to animate the green background to their new video for “O Valencia!” (http://www.mtvu.com/reanimatethedecemberists/)

On his show last week, Colbert said the Decemberists’ contest was a blatant copycat.

“Green screen? Hmm, where I have heard that before?” said Colbert, who plays a confrontational political talk-show host on the program.

He then issued “Stephen Colbert’s Second Green Screen Challenge,” challenging his fans to edit their leader into the Decemberists’ video using the same lightsaber footage available at http://www.colbertnation.com.

“Let’s see how they perform their trademark brand of hyper-literate prog rock when I’m slicing off their legs at the knees,” declared Colbert. “Oh yes, they will feel the pain.”

But Meloy, a charismatic and witty performer himself, hasn’t backed down. In an e-mail to music Web site Pitchforkmedia.com, Meloy and his bandmates responded: “We are asking our fans to help us win this epic battle. That’s right, we want you to help us defeat Stephen Colbert in our video!”

The Decemberists also upped the ante by proclaiming the first “Decemberists vs. Stephen Colbert Guitar Solo Challenge” and concluding, “Your move, Colbert.”

—

YouTuber OF THE WEEK: http://www.youtube.com/watch?v(equals)zbKyZOqpYSI

Everyone knows that YouTube has altered our sense of celebrity, boosting nobodies into minor stars. But could YouTube also serve as a last refuge for Hollywood’s B-listers? In this video, actor Jamie Kennedy (“Malibu’s Most Wanted,” “Son of the Mask”) parodies what it takes to “blow up” on YouTube. Kennedy mocks a number of YouTube’s greatest hits: Mentos in Coke bottles, the “Star Wars” kid, lonelygirl. The actor has documented the fluctuations of fame before – he wrote a memoir in 2003 titled “Wannabe: A Hollywood Experiment.”

—

DOWNLOAD THIS: “Star of Wonder” Sufjan Stevens

All 42 songs of Sufjan Stevens’ new five-disc “Songs for Christmas” are available on iTunes, including the singer-songwriter’s renditions of a number of traditional Christmas carols, as well as some new ones of his own creation. “Star of Wonder” is one of the latter, and it builds to a beautifully orchestrated climax. Indie musicians aren’t known for their earnestness, nor for their holiday cheer, but Stevens – who has made two albums themed to states (“Greetings from Michigan” and “Illinoise”) – long ago proved he marches to the beat of his own little drummer boy.