RING KING

To get unlimited stamina, try this sequence requires two controllers:
Press A on controller 2. Press A, Select and A on controller 1. Now 
press B on controller 2 and then Select on controller 1. Finally on 
controller 2 press A and B at the same time and then on controller 1
press B twice. Should work now! :)

Want to be invincible throughout the game? Then do this at the 
titlescreen:

1. Press A on controller 2, then press A, SELECT and A on 
   controller 1.
2. On controller 2 press B, on controller 1 press SELECT.
3. Press A then B on controller 2, then press B twice on
   controller 1.
4. Press START to begin the game.