SWGH, good idea. If there is any doubt in your mind, you are better off not using the Nintendo character in your game. It's a long project, and you don't want to break any copyrights by using a commercial character in your game. And also, you may one day consider distributing the game to others after it is built, and in that case, you can safely distribute the game or its code to others without any sort of possible legal ramifications.
