Sans doesn't look too different from classic Sans, the only difference is he has a massive hole in his skull right above his left eye socket, his shirt is slightly red in color and his teeth are yellowish color. However, this isn't Sans' true form. when sans gets angered, His eyes turn red and his ribcage opens up and turn into "legs" while his real feet fuse together to make a massive tail (or stinger). The "legs" and are shown to be bloody in most FanArt.