Beating the Final Boss:

 On his first form you have to hit the  coloured balls  on his arms. If
 you hit them they will  crack.  If he does  his move  where he  swings
 around  press Z  to stand on  your  tongue.  He'll hit your tongue and
 you'll  fall  down and you won't get hit, you'll also have a chance to
 hit his arm once or twice.  If you  manage  to crack  all the coloured
 balls his arms  will break off. He will then turn into a tank. He will
 then either  spin and shoot cannonballs or just shoot the  cannonballs
 straight.When he shoots straight grab as many as possible. Next,get in
 close and follow him until he does his spin around move.  When he does
 it jump over a  cannonball  and  use  machinegun  fire, if you hit him
 enough he'll die. If you don't hit him enough he'll regenerate back to
 full strength. 

Bonus Round

 Go to Stage 6 (Ghost Castle.) At the first room don't go up the stairs,
 instead go to the place near the  rabbit  and you'll see a locked door
 near a crown. Get the crown then open the door.  Go in to the room and
 you get to play a round of pool. 

     Note: You need at least 50 Crowns to get into the door.