Play as Nabbit and Mii in New Super Luigi U

Did you know that in New Super Luigi U for the Wii U you can play as Nabbit in single player mode On the controller, use the ZL trigger and play any level (or B on the Wiimote). Hold the Left and Right triggers and do the same method to unlock this secret. Being Nabbit, you are invincible and can still use almost every power of Luigi besides using power-ups themselves. This can be very helpful for beginners and safe lots of time beating the challenging version of New Super Mario Bros U. You can also play as your Mii but only in one level, the last level in single player mode: Superstar Road-9 Flying Squirrel Ovation.

Nabbit is a thief who steals items from Toad Houses and runs away with them in his bag. His appearance is that of a purple creature with round eyes, long ears, and black limbs. He also wears a white handkerchief with a drawing of a large mouth with sharpened teeth, similar to Bowser Jr.'s mask, as well as orange shoes and white gloves.

From Mario Wiki