Little girls sneaking out to be a puppy at the dog park after hours; completely nude as they run laps on all fours and gingerly play on the obstacle course. It isn't long before they're caught by someone taking their dog out for some late night energy burning.
The stud only wanting to play for a little bit before he gets a different idea, bowling over the little pup and humping away until the tapered tip catches on a hole and sinks in deep. Each rough thrust accompanied by a tinge of pain at the stretch and an accidental spurt of piddle onto the grass.
By the time the knot forces in, the bruised and numbed bladder has given up; the mind-breaking orgasm prolonged by more piddling between spasms.
In the afterglow the pup doesn't even notice the collar and leash being clipped on until the gentle tugging coaxes her along, dripping doggy cum behind as she goes home with her new owner.