You probably already know this, but on Super Mario Advance 4, when you continue your saved game or start a new game, you can choose whether to play a mario solo game or Mario and Luigi game. If you play a Mario and Luigi game, mario and luigi take it in turns to do a level. This is a cool idea because someone can choose to be mario and your friend can be luigi then you can both play using the same gameboy advance. Its a shame that noone has written a faq for this game yet, because I am having an hard time working out what the jap writing means.