[I DON'T OWN ANYTHING IN THIS VIDEO, IT BELONGS TO CARTOON NETWORK]
I've searched this music all day, and couldn't find it. So for you and me, here is the scene. It's from S02E03, "It's Time" episode.

This is obviously not my work, but you can watch what i do if you want. And for all the Regular Show fans : High Five ! /)

Oh, and if you noticed something at the end, it's this : http://fav.me/d6k8vf5