Level select: 

At the main screen with the ant hill, hold C-Up + 
C-Down + C-Left + C-Right + Z and press R. When entered
properly, an arrow will appear at the bottom.


Invincibility: 

At the beginning of a level, when the level description
appears, hold Z + R + L (the invincibility only lasts 
for the current level).


 Game Shark Codes: 

 Infinite Lives             801E1A38 0009
 Infinite Health            811E1A2C 0004
 Max Grain                  801E1A39 0032
 All FLIK                   801E1A3A 000F
 All Enemies Killed         811E1A26 0000
 All Levels Unlocked        81099150 000F
 Always Have Super Jump     811E1A28 0020
 Start with Blueberry       811E1A2E 0001
 Start with Homing Berry    811E1A2E 0002
 Start with Goldberry       811E1A2E 0003