[Video Games] Paper Mario 2 Bowser Level Block

I liked the game Paper Mario: The Thousand-Year Door. However I cannot figure out how to break the yellow block in the last Bowser level. It is surrounded by unbreakable blocks.




I’ve tried all the different sizes that Bowser can be in that level, and none seem to work. If he’s huge, he still cannot break the grey blocks, and if he is small enough to fit under there, his fire is insufficient to break it, and there is not enough room for him to pound-jump on it.

How do you break the yellow block? What is in there?