Super Mario Galaxy 2: Unlock and Play as Luigi
In Super Mario Galaxy 2 for the Wii, you can play as Luigi. At first you’ll only be able to play with him on certain levels once you gain 30 stars. Talk to him at the beginning of a level you see him on to take control of him, and beat the level with him to unlock a “staff ghost run” on that level, which you’ll have to be very skilled to beat.
Once you beat the game, a special door will open on Mario’s spaceship (on his forehead) and when you enter, you will be transformed into Luigi so you can play as him on any level.