These gameshark codes will modify Mario's size.
I suggest going half size or double size for a playthrough, if you want to do one.
812cb1ce 3E80 is his default size

Huge:
812cb1ce 3F00 is twice as big
812cb1ce 3F80 is four times as big
812cb1ce 4000 you'll be too big to even still play the game

Tiny:
812cb1ce 3E00 is half size
812cb1ce 3D80 is quarter size
812cb1ce 3d00 you will be a microbe and i don't think you have any shot at getting anything in this game like that
