This is a trade I did last October with my buddy  DragonKasaiRyu
There is also an alternate ending too for those that want a more explosive finish.

Alt Ending: https://www.furaffinity.net/view/59588900/

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It was a cold evening. The streets lit by lamp light, kids dressed in costumes running amuck in the streets. It was none other than Halloween. Dylan was out in his backyard though, buried deep into his work. Even with him being stuck under so much work, he at least took the time to be in his Lycanroc for. Even though his paws made it hard to work, he still wanted some sort of Halloween spirit.

While Dylan toyed away with his work, a certain someone watches him from the shadows. His friend Ryan just watches. Watching the Lycanroc work on his machines. Watching him build each one. Right in the center of the workspace, finished and ready to go, Dylan’s latest creation, The Feeding Machine MK3. A plan slowly forming in the Gengar’s head. A plan to enjoy it all while not even needing to put on any weight onto himself, but onto someone else.

He slowly slides between shadows. All while keeping an eye on his target. As he approaches the entrance to the shop, he peels his head in. Dylan has his back turned. The Lycanroc’s eyes locked onto one of his blueprints on the wall. So Ryan takes the opportunity and pounces. His body fading into Dylan, making him look around as he feels a coldness on his back. He turns around, his eyes darting around the workshop, “Hello? Who’s there?”

As Dylan’s eyes shoot around the room, he can feel himself starting to fade. His eyelids grow heavy as his head slumps low. He falls onto his butt before laying on his back. His breathing slows before he completely passes out. Not a moment later though his eyes shoot open. Though something is off, his eyes are no longer their golden yellow. Instead they are now purple and blue. A smile goes across his face, “Ahhh, feels rather interesting being in such a smaller frame, but it won’t be small for long. You and I are gonna have some fun Dylan.”

Ryan had possessed him, though the only sign of that even occurring to others would just be those eyes. Ryan takes hold of the new machine. It’s light and portable, with a separate tank, filled with a pink mixture. It was Dylan’s special formula. The formula that is incredibly dense in calories, and meant to make even the biggest of black hole stomachs feel full. Ryan lifts the mixture to his face, “Ahh, your wonderful mixture. Always using it to fill me up but can never get me full. Though now, using your body, I’ll be able to feel that fullness in spades.” He chuckles softly, before taking the tank and machine and wandering off into the woods behind Dylan’s home.

After about 20 minutes of walking, he comes to an open clearing. Dylan uses it for testing mainly. There’s many signs of those tests too. Knocked over trees, holes in the ground from some rather explosive tests. Even a couple forgot scraps. Ryan though was here for his own test. He sets the machine down and connects the tank to it. Pressing one of the buttons on top, the hose automatically shoots out and goes right into his maw. The liquid is already starting to flow in. The familiar taste of strawberry chocolate coating his tongue as he swallows it down.

Immediately as a mouthful of that stuff hits his gut, it immediately makes him grow a bit. His gut pushing out and growing softer to the touch. His legs and ass are gaining some softness too. A second chin also starts to form on his face as he lets out a soft moan. Each gulp expanded every part of him more. Even though it’s not his body, the feeling is still as euphoric as ever. Just like every time Dylan has him gulp on this stuff. He rests his paws on his gut. Feeling it churn away at the formula as his gut grows with each gulp, groaning and gurgling as he forces his possessed body to grow.

The tank reaches about a quarter empty before Ryan has to sit. His frame became too heavy to keep standing. He presses his paws into his growing mass of a gut before giving his moobs a squeeze. He looks up and lets out a long breath. The feeling is still just as amazing and he can feel something. A light feeling in his gut. The feeling of fullness, it was far off but it’s there. He can feel it. His gut continues to slowly swell forward in front of him as the tank and pump rest atop his gut. He looks back and sees his growing ass too. His legs, now useless to him as he feels his feet sink into the rolls that are his legs. He squeezes his chest once more as he can feel that fullness approaching slowly.

As the tank starts to approach the 50% consumed, his arms have since sunken in. The tank and pump now nestled in between his moobs as his ass presses against a couple downed trees behind him. His gut starting to take over about a third of the field too. Most importantly though he can feel the fullness in his gut. Now taking on a bit of a tightness as it starts to stretch to accommodate the growing liquid building in it. Ryan can’t help but tank softly as his head slowly sinks into his mound of cheeks and neck fat, “This feeling… this tightness… I’m starting to feel it… the sense of fullness… it feels so good… more…”

The tank soon reaches its final quarter. Ryan’s gut about 100 feet from the far tree line while behind him, his ass has already toppled new trees. His paws, feet and head now fully sunken into his mass. His gut rumbling and gurgling as it processes more of the formula. Making him further grow more. Though occasionally there’s a new sound. A light creak and the occasional groan. The fullness was growing into a tightness. The feeling of reaching a limit. He could only muster a few muffled sounds as he gulps down more of the formula. A growing desire for more. To feel that tightness grow.

5% of the tank remains, the gurgles and groans now long since drowned out by the sounds of creaks and groans as they grew longer and louder. This was the feeling he desired. The trees behind him had been flattened by about 100 feet past the start of the field and the tree like to the front of him was now starting to be pushed back too. Even the line on the sides too. On top of that, he was now visible above the tree line too. Anyone passing by the forest can see the fluffy mounds of white and navy blue. A new question now was flooding Ryan’s mind, can he handle the rest? Could he? Would he explode? His mind raced with the thoughts, and even if he did, not like it would do anything to him.

The final 5% was a rush of emotions. The first two percent were more intense feelings of fullness and tightness. The creaks growing ever louder as he feels more trees falling. His paws, feet and head sinking further in as all he can hear are the creaks. The next 2 percent came with confidence, thoughts of being able to handle it. Though the final percent really threatened to burst him, his hide unable to stretch more but just managing to find its way in and keep him held together. He sits there as the hose automatically retracts itself, feeling every inch of him filled to bursting. Finally able to feel what it’s like to be full, all thanks to Dylan’s body.

After enjoying the feeling for about an hour, he finally relinquishes Dylan’s body and floats above his about-to-burst blob of a friend. Looking at all the forest he destroyed too. He lays himself gently on the gut of his friend as Dylan comes to, woozy before immediately feeling the rush of tightness. Ryan chuckles softly, “So this is how it feels to have the roles reversed, I see why you love it so much.” He rubs Dylan’s gut before floating off, “Have fun trying to get yourself out of that situation!” Before vanishing into the darkness of Halloween night.

The End!