The Patapons need a siege weapon to destroy the castle in Mt. Bachikoi. Start off by killing the Zigotons and the wall without destroying the catapult. When your Patapons touch the catapult it will automatically become yours (if you have good Kibapons, and you're good at keeping Fever Mode, it is a good idea to bring them along). You will need to attack more Zigotons and a few towers all while not destroying the catapult. You will use the catapult to kill them (the catapult fires at the Zigotons on its own, but you'll still need to protect it well by keeping your troops at a safe distance).