To change the world just unlock and beat every level in the game and go to the special world and go to the second star at the end of the world and press A while on it and every thing will change. the worlds will be red, turtles are mario bobble heads, bullet bills are birds, and goombas are pumpkins.(ive never done this myself but i saw a friends game and everything was changed).if you do this theres no going back(exept if you dont save and turn off the game), it will never be the same so if you want to keep it regular than dont do what i said above. maby you should save before doing this and do it and see if you like it this new way or the old way.