Nightmare Suicide Mouse was a antagonist in Five Nights at Treasure Island: The End of Disney.
He appears to have sharp "teeth" in his eyes and mouth. He's also missing his right ear, and has human-like eyes.
He'll walk around the building at random and eventually appear at the left office exit. Shining the light at him will not make him go away. To get rid of him, the player must pull up the monitor and shut off a camera. Failing or neglecting to do so will make him attack the player.
He starts off camera before appearing on CAM 03, then move to CAM 01, CAM 02, and then the right door of the Office. If the player fails to shock him quickly, Suicide Mouse will jumpscare the player and cause a game over.