It was subtle at first, despite the pressure. In fact, the Meowth felt close to nothing, save for exotic tingles arcing through his body, as thought the weakest of lightning bolts were pelting his flabby frame. In fact, it almost felt... good.
Then, quite suddenly, it kicked in, starting from the very tips of his toes. He watched in awe as each little toe swelled, claws remaining sheathed throughout, though the opening seemed to shudder and heave, raw fat sinking into the pores of his toes. The sight was grotesque to behold, each bloated digit easily larger than the rest of his feet... at least, until they too would grow. Each paw pad grew plump and saggy, accenting the heaving mounds of flesh that became his paws. Even if he was presently obese, his very feet had evolved into a gargantuan mass in a very short amount of time.
His front paws and limbs soon followed suit, arms 'n legs bulking up in a manner most foul, the sound of bubbling heard beneath his flesh as fat piled up upon itself, giving each arm and leg an exceedingly chunky appearance. His paws became useless, holding them up to his face to watch each finger become fat sacks of flab, much of it sinking into the clefts that hid his claws. He could barely flex or move any of his digits, awakening a nameless fear in his heart. He then discovered it was not fear he felt, but a sickening sensation welling up in the pit of his throat, or rather, in the back of his mouth. Sweat built up on his 'brow, beginning to pant... He didn't feel well.
The sensation grew and grew 'til he could contain it no more, his maw stretching wide, wide open to deposit a massive amount of... saliva!? Yes, his very palate and saliva glands had grown to the size of watermelons, generating enough drool to constantly wash over his body in a constant stream, sinking into the rolls of his growing gut before his eyes. The very waves of drool seemed to awaken the growth of his belly and butt, cellulite manifesting in pound after pound of weight.
Within short time his tummy easily became the largest aspect of his chunky frame, fat legs stretched around the sagging sphere of suffocating substance. Multiple rolls of fat laced across his gut like a meaty lengths of garland, his behemoth button sticking out like a hairy dome. Nearly matching the overwhelming size of his gut was his ample pair of buttocks, each flabby mountain accented by his only mildly affected tail, the curled up length now nothing more than a straightened out pole of fat.
The fat Pokémon was having trouble breathing behind the weight of his body and the constant outflow of raw saliva, puddles of drool pooling up around his obese body. Topping off his transformation was his head, starting with his neck - the formerly short and neat pole now littered with rolls upon rolls of flesh that, along with his many chins, spilled out over the top of his torso. Each cheek soon tried to sag toward the ground, not so much from fat but from the drool constantly developing in his body.
Now thoroughly fattened and immobile, Meowth felt the pressure leave his body, giving him a moment's respite to recover his senses. Every pore in his body screamed, the heat of his body squeezing out dollop after dollop of moist sweat, mingling with the multitudes of drool slopping out over his body at any given moment. Though he felt vulnerable in his behemoth form, he felt somehow... good. So good, in fact, that he felt the urge to stand up. One... two... heave! Somehow, someway, the massive Meowth managed to stand on his two wobbly legs, barely able to support his weight.
He was glad to know he wasn't fully immobile, but he now he needed to make some decisions, such as what to do next. Unfortunately for him, his body began to make decisions on its own, stomach rumbling and growling with sudden anger, the oh so familiar pressure returning. Was he going to grow again? No... that wasn't it. His stomach was telling him something.
... What could it possibly be?