Kind of hard to explain this quite frankly....lol

This is sort of a cheat, but more of an in-game exploit. No out of game devices needed, except tape. lol

Anywho, in Chapter 5, I forget which section, I think the third part, there is a place with a pipe that spawns enemies. The Flower thingies. It is hanging from the ceiling. Next to it, there are blocks on either side, each one about level with the base of the pipe, maybe I little lower.

Get on top of one of those blocks with Bowser after defeating the flowers waling on the ground, and start breathing fire. When the pipe begins to re-spawn them, Bowser will defeat them as they pop out of the pipe. Tape down the down button (when playing with the remote sideways) after on the block, so he will continually defeat them.

Check back periodically in case you level up so the game will continue.