His appearance is similar to Undertale Sans's. His left eye twitches whenever he kills people. He has blood on his mouth, scattered throughout his teeth. Insanity Sans has an unusually large smile, so large in fact that it meets with his eye sockets. He has unusually small pupils that shake from time to time. He has wounds in some parts of his body, indicating the areas where his victims tried to attack, most notably his head. It has 4 cracks because it is the most practical area to strike.