Fun fact. Undertale's concept art shows Sans to actually not have a shirt on. His sprite was mad even at the time of this idea. But for his battle sprite they decided to give him a shirt. HOWEVER, I actually think he DOES put his shirt on in the times he shows up in the battle menu as we never see his overworld sprite before it switches to battle mode. Pacifist, we never see ANYONE. Genocide, he's just a silhouette.