In the Plantation stage go to the "Rest Area" in this room go to the bottom where the water is, and go left through an opening in the wall until you reach an outside area called the "Inner Wall"* This place is dangerous and you will need the booster 2.0 for it. Struggle your way (and I mean STRUGGLE) to an area where you see a door at the bottom left but there is a wall between it, go under the wall and boost upward until you get to that door, once inside you will enter a "Secret Grave" with a huge "Prinny" statue at the center, examine the sparkly object to get the "Prinny Cap" this can be equipped over your existing cap. *Note* if you fall at anytime while in the Inner wall area its counted as a game over just like the "Outer Wall" stage, so make sure you save where you see the save points.