New Super Mario Bros. 2 (3DS)
Play as Luigi
After clearing Bowser's Castle in World 6, you can play as Luigi by holding the L and R buttons while choosing the file on the file select screen.
A new "save" option will replace "quick save" on the map screen menu after you clear World 6.
Unlock Coin Rush mode
Clear World 1-Castle to unlock the Coin Rush mode.
Save file stars
Here's how to get each of the five stars to appear on your save file: