If you've never heard of it, there's a maximum security prison in the Philippines where the prisoners have to DANCE as part of their rehabilitation.

You might remember them from the huge choreographed "Thriller" dance they did back in 2007.

This time, hundreds of them did the "Gangnam Style" dance  in the pouring rain.  The video was posted on YouTube over the weekend, and it already has over a million hits.

Their original "Thriller" video now has over 50 million.

Here's the video: