Junior Martial Arts Demonstration Quickly Devolves Into Dance Battle

I’m not sure what this is, or where it is from, but it appears to be some sort of prank that junior martial arts competitors are playing on an unsuspecting audience. What starts off as a standard match between two kids, quickly turns into a very funny dance routine. I know that the trainers were involved and probably thought it was a great idea. However, in my imagination, there is a really pissed off sensei screaming “Sweep the leg!” from right outside the view of the camera.