If your starting the game,find & finish all areas,
fortresses,castles and secret areas to unlock the cheat.
You will see a short movie that Mario & Luigi are replacing shells to Mario & Luigi head costumes that
Koopas are wearing(Not the boss Koopas).Your enemies will change too.The islands that you completed will be
change into many different colors.I completed this cheat twice.I hope that my cheat will be useful!!
:)