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.

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

Longer preview: