Xbooru - 2010s 2017 2boys animated skeleton artist request big dom big dom small sub bigger dom bigger dom smaller sub bigger penetrating bigger penetrating smaller black hair blue blush blush bottom sans completely naked completely nude grabbing arms hair over one eye humanoid humanoid robot larger penetrating larger penetrating smaller legs spread licking licking head male male/male male only male penetrating mettasans mettaton mettaton ex nude penetration pink blush pink eyes robot robot humanoid robotic penis sans sans (undertale) seme mettaton sex skeleton small sub small sub big dom smaller penetrated smaller sub smaller sub bigger dom spread legs sweat top mettaton trembling legs uke sans undead undertale undertale (series) white background yaoi