Rule 34 Dev - anal anal_sex anthro balls bulge deep_throat dr._eggman duo echidna erection fellatio human human_on_anthro interspecies knuckles_the_echidna male male_only mammal matainfancias monotreme musclegut muscular muscular_male navel nipples oral penetration penis sex simple_background smile sonic_(series) white_background yaoi|3210650912