Get 15 stars so you can access the first Bowser. Fight him and gain the key to the basement. Go to the basement and catch the yellow rabbit. Now, use the Bring the bunny around the castle trick to bring him to the lobby of the basement (just go through the entrance to the area where you found the bunny). Now, bring him to the 30-star door leading to the second Bowser. This part is rather difficult (and frustrating because of the constant "you need 30 stars" message - but don't give up, this is doable!). Place him just in front of the door and stand a bit behind him, facing away from him. Now, do a jump and tilt the control stick in the direction of the bunny so you jump backwards. You should land between the bunny and the door. Keep on jumping like this, sometimes having to reset yourself to behind the bunny, and you should eventually get popped through the door by the bunny.
Now, enter Dire Dire Docks and get a star to open up the 2nd Bowser. Fight him and gain the key to the upstairs. Go upstairs and then go to the stairs leading to the 50-star door. Use the Supersonic speed to get you through walls glitch to get up the stairs, through the star door. Now, go to the endless stairs and use the same supersonic speed glitch on the endless stairs. You should be at the final Bowser. Fight him, and you will have beaten the game with just 16 stars! You also don't need to have gotten any of the caps, and even without the wing cap, Mario will still fly around in the ending scene.
Submitted by: Dom Dunc