Things To Do After 120 Stars
I know that after collecting all of the 120 stars in the game, you can blast yourself from a cannon onto the castle roof, where Yoshi will give you 100 lives and a new, special triple jump, and you can race a fatter version of the penguin down the slide in Cool, Cool Mountain.
But is there anything else that's brand new in the game after the 120 stars have been collected?