Rule 34 Dev - 2010s 2016 2boys 2d 2d_(artwork) animated_skeleton bigger_male biting_lip black_and_white black_hair blue_jacket bottom_sans clothed digital_media_(artwork) ectotongue fellatio genitals hair hair_over_one_eye hand_on_another's_head hand_on_head heart humanoid humanoid_robot jacket ladybumtickler larger_male licking licking_penis line_art lineart male male/male male_only mettasans mettaton mettaton_ex monochrome monster oral penis robot robot_boy robot_humanoid sans sans_(undertale) seme_mettaton sex size_difference skeleton smaller_male sniggysmut third-party_source top_mettaton tumblr_username uke_sans undead undertale undertale_(series) video_game_character video_games white_background yaoi|1023803