he is a skeleton, he is homicidal and loves to kill, he does not question himself because he lacks the ability to feel confusion, he never cries and his eyes normaly glow red, or white or flash blue and yellow and red, his brothers skull has tears on his face, he wants to kill you, he calls himself sans, he talks to himself and his brothers skull often, even infrount of other people, he often says to his skull after hes killed somebody "earnt you proud of me, papyrus? HAHAHAHAHAHA!"