Xbooru - 1:1 1:1 aspect ratio 2010s 2016 2boys 2d 2d (artwork) animated skeleton bigger dom bigger dom smaller sub bigger male black background black hair blue hoodie blue jacket blue tongue bottom sans clothed dark background digital media (artwork) duplicate fel-fisk glowing hooded jacket hoodie humanoid robot jacket larger male licking lower resolution duplicate male male/male male only mettasans mettaton mettaton ex one eye closed partially clothed partially nude pink eyes pink slippers pink tongue robot robot humanoid sans sans (undertale) seme mettaton sinisk skeleton slippers small sub small sub big dom smaller male smaller sub smaller sub bigger dom soul soul sex sweat tongue tongue out top mettaton uke sans undead undertale undertale (series) video game character video games yaoi