That's the ending credits song. Patapon doesn't have a typical soundtrack. Patapon is kind of like a side-scrolling RTS and rhythm game hybrid where you give commands to the Patapons by playing drums using the face buttons on the PSP. The Patapons sing in response to your commands, creating a unique song for each playthrough of each level. "Pon-pon-pata-pon!" (or circle-circle-square-circle), for example, is the command for attacking enemies. It's a very interesting and fun game series but it's less fun when you're not the one playing it.