Mr. Resetti is a NPC from the Animal Crossing series of games.
He is meant to discourage players from resetting the game or shutting off their system without saving. If you do happen to either of the two, Mr. Resetti will come to your house and lecture you on the importance of saving. Do it enough times and he will even do a "fake" reset on you, actually playing a joke on you.
Mr. Resetti has a brother named Don Resetti, who is the exact opposite of him.
