This is an official ending to Sonic Underground... but you may not know that for obvious reasons. It only played in the Mexican version of Sonic Underground and only played at the end of episodes 30-33. It was the version 2 of ending 2 (that can be found here https://www.youtube.com/watch?v=JQQggttS7uA&list=UUQLVTT8LkgSOyZ2mD8BU3dA&index=2) that played through episodes 20-30, but this only made it into the final versions of episodes 30-33 instead of episodes 30-40 like was originally planned and was removed from the rest for unknown reasons.