Fernando is a big dog. A mix between a husky and a golden retriever, he's very much on the larger side as far as dogs go. He loves his owner, of course, even if he doesn't quite understand what he's trying to say most of the time. He loves his owner so much that he can't help but wag his tail and bark a hundred questions at him as soon as he walks in the door. 
His owner, an anthro deer named David who has just recently shed his antlers, is just as eager to see him. He bends over and gives lots of pets and affection to the dog, though he of course ignores his questions. Fernando leans into it eagerly.
"Looks like you didn't make a mess in the house, not even on the newspaper," David observes, "Good boy! Do you want a treat?"
David of course doesn't quite understand Fernando when he tries to explain that he can't hold it for as long as David tends to expect him to, but he can always forgive that. He barks in excitement as David moves to the kitchen and gets out the bag of dog treats.
Fernando rushes after his owner eagerly at the sound of the treat bag rustling, bolting headlong into the kitchen. However, his burst of speed is a bit much for indoors, poorly calculated in his excitement. There's a thud as David falls back onto his rear end, having slipped from the sudden sound of dashing paws making him jump. At the same time, Fernando crashes right into him, ending up with the deer's muzzle directly in his maw. 
Both sit for a moment in stunned silence, and David's head slides just slightly further in.
GRRRRMMBLLLLE
Fernando may have his heart in the right place, but he's certainly not the brightest. With the delicious taste of deer in his mouth, a treat on his mind, and hunger in his belly, he glances at the deer poking into his maw and gulps. "Oh, he's tasty! I didn't know that," he thinks, in his shock not quite grasping what he's actually doing, "I guess he'll do."
GULP ULK SHLRP
David attempts to shout at the dog, but his muzzle is firmly held closed by the inside of Fernando's throat. Fernando gulps again and again and again, each time bringing him closer and closer to the dog's hungry belly.
The disoriented dog is deceptively quick at swallowing his owner, and within 30 seconds...
ULP! GRRRGLE GLRRG
Fernando rests on a very, very tight gut full of David. Then he finally starts to process the situation. He'd never hurt his owner, but it did feel good, and well, David doesn't seem to be complaining. This is not considering the fact that David is held so tightly he can't move a muscle to struggle or to shout, but after such a hefty meal, such a mistake is surely forgivable.
With the deduction that this must be okay, Fernando decides to have some fun with his owner while he's still inside. The dog leans as far forward as he can, pushing the massive bulge back right under his crotch. He presses his erect, knotted member up against the bulge and starts humping, panting eagerly as he does.
GWWRRRRGGG PLAP PLAP GRRRRGLLLE HUFF HUFF HUFF
Fernando grinds on his trapped, melting owner for a long while until he finally shoots a thick load of cum into his own belly fur, panting heavily on top of a bulge that is now much less defined. He scoots back centered on top of his gut and decides to take a nap, now that he's expended so much energy.
As soon as his nap has ended, Fernando maneuvers over to the newspaper. It is't terribly easy with such a massive gut, but he manages.
FBLRGLRRGRGBLLRGRRLL PLAT FBLRLBRLFGG
Though he can't quite squat like this, with some effort, he gets the first of many massive, bone-filled dog turds out onto the paper. 
FLLRBLRBGLRLBRLBBLLE HUFF HUFF BLRRBFFLLRT FSSSSSSHRSHHHFSSSSS
The mound of dog shit and bones that used to be David only grows as Fernando's doggie gut shrinks. The moment his gut is small enough to no longer get in the way of his cock, he begins to let out a stream of urine comprised of water from his bowl earlier in the day and David's bodily fluids after a trip through the dog's digestive and urinary systems.
A sizeable pile of crap builds up behind the dog as it empties itself, some of it spilling out off of the paper and onto the floor, as is inevitable with so much shit. Finally, only David's pelvis is left inside the dog. It takes some real effort to shove the whole thing out his tight hole, but Fernando soon finally manages.
FLLBRLLRBLL HUFF HUFF HUFF NGFHFF- SPLAT!
The pelvis lands in the giant mound and sends a small spray of dog shit onto the floor in all directions. The dog gets a bit of it on the back of his legs as well, but he thinks little of it.
Fernando trots off with a wagging tail, delirious from the ordeal but very, very satisfied. "I used the newspaper," he thinks, "I'm a good boy."