When battling your friends choose the last stage. Get a fire mario and stand on top of the space where only a mini can be in. Kneel down and keep on jumping, when the top comes down it will push you through the floor giving you a chance to take some stars if your opponent is in there. =p
While selecting file 1,2 or 3, hold the L+R buttons and select it, you should hear luigi's voice and he says: "Luigi"
when your on the map choosing the world pause your game when your on the map and press l,r,l,r,x,x,y,y and it will turn on the secret challage and the thing about this mode is u can never go left just keep going right
if you put in a freind code the name is not permanet once you go on WI-FI the name is changed to the real name :)
For this to work you must be Giant Mario or Luigi use a giant Mushroom and hit the pole it will break and you shrink and beat the level
When you finish a level the following may occur:
1) If your time ends in x11 x22 or x33 etc. you'll get fireworks (depending on the number, 11 = 1, 22 = 2, etc.) and the end level theme from the original SMB.
2) If you hit the very top of the pole or hit above and drop on it you will recieve a 1UP.
3) Or you can receive up to 8000 points. (Both this and #2 apply to #1)
To be able to save anywhere in the game, simply finish the game once. You'll recieve a star next to your save file and there you have it.
On the file select screen for single player mode hold L + R and press A on your file to play as Luigi.