Xbooru - 2boys 2males animated skeleton blue blush blue penis bottom sans clothed cute penis ectopenis english text gay grey background groping hooded jacket hoodie humanoid humanoid robot jacket leg between thighs looking away male male/male male only mettasans mettaton mettaton ex monochrome monster partially colored penis penis through fly robot robot humanoid sans sans (undertale) seme mettaton shirt lift shirt pulled up shirt up simple background skeleton small penis solid color background sweat text text bubble top mettaton uke sans undead undertale undertale (series) unknown artist yaoi