Boss Analysis

The boss battle that I analized was Super Mario Sunshine's Petey Piranha Strikes Back. The way this battle is introduced to the player is when you first jump off the windmill onto the roof.

The moment you touch the roof, a cut scene begins. Both Petey Piranha and Mario look around confused before the rooftop crumbles below them. The camera cuts to look up at the roof as it caves in with Mario and Petey Piranha falling past the camera. Once they land, the battle begins! 

 

Petey immediately starts spitting out toxic sludge. In his sludge, the first of his minions comes out.

The little white guy in the image above (usually a transparent green, blue, or red color. When they are getting ready to attack you, they start flashing white) can come out whenever there is sludge on the ground. So not only do you have to pay attention to ol Petey over there, but these little guys too. You can get rid of the sludge by shooting it with your water. If you let it build up too much, the dark creature in the image below will appear out of the sludge and fire sludge balls at you.

Now to fighting Petey. Obviously you have your water companion, so you start shooting him with water. No where is it explicitly stated that you shoot water into his mouth, but after some experimentation of shooting at him, you realize that's the only thing that causes a change for him (he starts flailing and getting fatter). When you fill him up with water, he falls on his back and a red arrow appears above his belly button, very conveniently telling you where to hit him.

After jumping on him three times, he melts into sludge and a cool golden star appears (mine would be gold but I already got it so its translucent blue) and you have officially beaten the boss! 

Mechanics:

The basic mechanics for this level are shooting the water, using the hover nozzle to get around, and slamming Petey on the belly button. 

The mechanics aren't really integrated into the level layout or the level art. The mechanics are in the way that you fight the enemy AIs. The hover nozzle will allow you to fly over both of the minions (even if the smaller one is jumping) for quick kills and cleanup. 

Unlike a lot of boss battles, this one doesn't get any harder the more you damage him. Of the three times you slam him, he is always the same difficulty. The only thing that really changes is how much sludge is on the ground, but that is mostly dependent on how much and fast the player can clean up. 

The reward is a golden star which is the main thing you collect in the game. 

Here is the basic level layout:

and a link to the pdf version of it: Petey Piranha Strikes Back Level Layout