Super Luigi
Luigi is Mario's younger brother. He helps Mario during some of his quests to rescue Princess Peach. You can play as him by holding the L and R buttons in the back of the DS while selecting a file.
Luigi's Power Forms[]
Standard Luigi[]
This is how you start out in the game. Taking a hit from any enemy will cause you to lose a life.
Super Luigi[]
Grabbing a Super Mushroom allows you to grow bigger. This will let you take an extra hit from an enemy, and you can also break blocks.
Fire Luigi[]
If you get a Fire Flower you can transform into Fire Luigi. You can throw fireballs at enemies, and destroy most of them. You can take 2 extra hits from an enemy. This power-up helps in boss battles.
Shell Luigi[]
If you find a Blue Koopa Shell you are able to transform into Shell Luigi. You can Shell Dash to break bricks from the side and take out any enemies along the way. You can also hide in your shell and enemies can't attack you. However, if you hide in your shell during a Boss level, if the boss touches you you will get knocked out but still have it.
Mini Luigi[]
Probably the most dangerous power-up in the game, getting a Mini Mushroom lets you turn into Mini Luigi. However, taking a hit from an enemy causes you to lose a life. But, there are some advantages. You are able to bounce on enemies, and you can fit into tiny passages and access tiny pipes only available to Mini Luigi.
Mega Luigi[]
If you can get a Mega Mushroom, you will grow to ginormous size and you can smash through enemies, blocks, and even Bullet Bill Cannons. However, touching a Tower/Castle hazard (e.g. Spiked column, closing wall) will cause you to shrink to normal size. You will always return to Super Luigi, even if you had a Fire Flower or Blue Koopa Shell before. However, if the area Luigi is in is too short when he gains this, he will shrink back to Super Luigi (Or Fire Luigi or Shell Luigi) and the Mega Mushroom goes back into your pocket.