alternate_universe bodily_fluids clothed clothing digital_media_(artwork) duo fan_character femboy hair hi_res humanoid long_hair machine male male/male mettaton mettaton_(underfell) mettaton_ex mettaton_ex_(underfell) multi_arm multi_eye multi_limb not_furry open_mouth robot sharp_teeth simple_background square_crossover tears teeth underfell undertale undertale_(series)