anal anal_penetration anthro anus ball_stretching barefoot bound bucket canine clenched_teeth cock_and_ball_torture defecating dog erection feces flat_colors fully_bound humanoid_penis male mammal pain partially_retracted_foreskin pawpads penetration penis rope rope_bondage rottweiler scat scrunchy_face signature solo straining suspension teeth toe_bondage toothpasta uncut