On December 15 (KST), the American rock band surprised K-Pop fans by uncovering a special version of "Champion" featuring the top Korean idol star. The unexpected collaboration of the two artists came as a great surprise, and also a delight to many. 

It's not available for download in the United States but in other parts of the world, where it's currently December 15, you can download it on iTunes.

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You can listen to a preview of the special collaboration below. 

Longer preview: