Nabbit

Nabbit is an enemy introduced in New Super Mario Bros. U. It is a thief who steals items from Toad Houses and runs away with them in his bag. The player can find them in various levels. When the player finds Nabbit, they must chase him throughout the course. When caught, Toad will take the P-Acorn out of the bag and give it to the player.

The bandana it wears resembles the one of Bowser Jr. and it also steals items from Toads so it likely has an affiliation with the Koopa Troop.

Trivia

 * "Nabbit" is a play on the words "nab it" and rabbit.