Happy Mouse is a antonigist in Abandoned Discovery Island 3.0.
He appears to be a demonic or distorted verison of Suicide Mouse. He has a human's jaw. He is smiling and his hands are behind his back.
Happy Mouse starts in the Broadcasting Room, and when he is active, a demonic and slower verison of Suicide Mouse's music can play. Then he goes to Character Prep 1. Then he goes to the Meat Freezer, Office and then Character Prep 2, If you don't do anything when he is in the office, he can jumpscare the player with a killscreen which shows him close to the player in the game over screen of the game "Happy Mouse". The jumpscare can crash the game.
- He is one of the suits with a human jaw.
- He is a character in FNATI 2: Let the Show Begin
- His jumpscare is actually the game over screen from the game "Happy Mouse"
- He obviously smiles, because "Happy Mouse" is his name.