Nabbit is a villain from New Super Mario Bros U. He also appears as an anti-hero in New Super Luigi U, replacing Mario.
Nabbit is a peculiar purple creature with ears resembling those of a rabbit as well as having the creature's speed. He carries around a big bag with a Mushroom icon upon it for snatching items. He also wears a white handkerchief that bears the illustration of a mouth full of sharp teeth as a mask, resembling that worn by Bowser Jr..
Nabbit steals from Toad Houses featured in the game and appears in seven of the game's levels. In order to acquire necessary stars, Mario must pursue and capture Nabbit in order to retrieve the stolen goods. In each of his appearances, Mario tracks Nabbit throughout the levels in question and catches him. Afterwards, Mario will punt Nabbit out of the level and return the stolen goods to Toad, who will give Mario a P Acorn as thanks. Should Mario fail to catch Nabbit three times, the thief will disappear until the conditions for his reappearance are met.
Nabbit also makes an appearance in enemy stages throughout the game. Should Mario take too long to retrieve his treasure earned for defeating the enemy, Nabbit jumps in and robs it.
In New Super Luigi U, Nabbit appears in place of Mario and appears to be an ally of Luigi's throughout the game. However, Luigi still has to chase Nabbit down in the sections devoted to catching him. And even though he seems to be on Luigi's side, it doesn't stop Nabbit from stealing Luigi's treasure if he takes too long to collect it.