To free them you have to find a key on each level that opens a cage containing colorful pequepos pequepones.
On each setting you'll find different friends that can't be eliminated, meaning you'll need to avoid them by jumping over them with the space bar.
On the last level, you'll have to kill Panzapon by throwing objects at his head. This will liberate all the patapons from his evil intentions.
Patapon is a highly recomendable game if you want to spend some time without too many complications or imposible game modes.
In the unregistered version you can only play the first five levels.