The household was quiet, all the mons were sleeping in their represpective rooms and beds, but for one, Umbreon. This sneaky pokémon loved the night and usually just slept trough the day to wake up and live trough the night. It never bothered any of the other mons much, they got used to it, but that gave Umbreon the advantage of moving around the house without anyone minding it, and thus he got a wicked idea one night. Umbreon and most of the other mons in the house were into inflation, and one of those that weren't was the young Eevee that always found it dangerous and uncomfortable, that wasn't enough for Umbreon though, and so he decided that tonight he was gonna grab one of his smaller much quieter air pumps and pump up Eevee to his limits. Umbreon knew of most of the mons limits, even those that weren't into inflation, they at least tried it once, but Eevee always refused, seemingly really embarassed about the fact he should be inflated like some balloon or whatnot.
Umbreon quickly made his way over to the Eevee's room unnoticed, small air pump in his paws. 
He didn't waste a second and quickly yet gently pushed the hose in Eevee's tailhole. Eevee was in slight discomfort but kept sleeping, oblivious to what was about to happen to him next. 
Umbreon took the pump and pulled the piston all the way up before pushing down on it forcefully, the full pump making the Eevee's belly rumble. Umbreon cotinued building up pressure inside the poor Eevee's tummy, making it rumble from time to time with how quick the pumps were. The Eevee was in obvious discomfort now as it kept turning around and shuffeling in it's bed before waking up. As he opened his eyes slowly, he could feel and hear the rumbeling clearly and loudly, looking at his tummy he noticed it looked slightly bigger, but was hoping he was just imagining things. Yet when he tried to sit up he realised that it was not just his imagination, as Umbreon quickly held and forced Eevee to lay down again. One paw over the Eevee's maw and head and the other on the pump, trying to calm down Eevee with his soft yet smug voice "Shhh, don't worry, just lay down and let me do my thing, once i'm done you can go back to sleep~" Eevee couldn't protest even if he wanted to, as Umbreon was at least one time his size, easily overpowering the Eevee into laying back down. Umbreon kept pumping and pumping, Eevee's belly finaly starting to show the fact it's growing as a small strech mark shows up on the taughtest place under the pokémons fur, Umbreon clearly enjoying the sight, the Eevee slightly disstressed. He just could yell out or something so that the other pokémon would wake up and come help him, but Eevee would be lying if he said he wasn't at least slightly enjoying it. He didn't like the pain, taghtnes, or the pressure, he liked seeing himself grow and be big, it was oddly satisfying to him, and so he let Umbreon continue. 
A few minutes pass and the taught, pressuring and slightly painfull feeling has moved to almost all of the small pokémons belly, it looked like a smaller soccer ball, it was tight and hard, but the Umbreon knew he could sneak a few more pumps inside. Grabbing the pumps piston in one paw and using his other free paw to place on his friends tummy and feel it grow, pumping slowly to not cause too much discomfort to Eevee, who was squinting his eyes from discomfort. Eevee was still tired, and closing his eyes and going to sleep sounded so beutifull to him, but he was worried Umbreon might get too carried away and pop him while he's sleeping, besides, seeing his belly overgrow and hide the lower part of Umbreons body from Eevee's view was really satisfying. The gentle rubs Umbreon gave Eevee calmed his belly to some extend, not too much though as Umbreon was still pumping. The small mons belly creaked slightly with every slow pump pushed inside, it wasn't discomforting anymore, just really tight, wich Eevee got used to pretty quickly. When Umbreon saw that Eevee's neck fur was now basicaly covering his face, he decided that might just be enough. He finished the last pump wich made the Eevee's belly shake as it was now really close to popping. Umbreon placed down the pump and used both of his paws to massage the small mons huge belly. "Now that wasn't so bad, was it?~" "S-Sush up, you're lucky i didn't call for others..." Umbreon sighed and an audible *plop* could be heard as he pulled on the hose, pulling it out of Eevee, gathering up his pump, and quickly disappearing back into the night.
Eevee just laid there, placing his paws on his oversized tummy, and rubbing it just like Umbreon did, it really felt comfortable and satisfying, he felt his size all over, pressing on it just to feel how tight it really is. As much as the small mon didn't want to admit it, he liked it, he liked every last bit of todays inflation, and so satisfied and happy he went back to sleep, hugging his belly as he drifted off.