Pigma

As if he couldn't get any uglier, this pig isn't easy to beat. Destroy all his hands first to get past the first phase (on silver and gold difficulties you'll know the almost destroyed when the inside turns red). To finish Pigma off, attack his face when its revealed.

Meteo Crusher

This monkey his not going to be easy since there is three phases of battle. First, aim for the yellow triangles that appear while his shield turns, then aim for the yellow diamond in the middle of where his shield was. Finally, shoot the yellow rectangles when turns the back of the ship on you to win.