Ok, if you're Jigglypuff, go to Bridge of Eldin. Make sure Smashballs are on, and get one. As soon as the middle of the bridge blows up, wait for the ship to appear. After it STARTS to reappear, go into the middle of the Black stuff and press B. Now, you will start growing large, but you find out that when it regenerates, you will be LARGE JIGGLYPUFF! Enjoy the awesome trick.