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The man awoke in a strange chamber full of mysterious machinery. He was strapped to a plush table which leaned back at a 45 degree angle. The binds on his hands and feet didn't budge, and he was tied naked and spread eagle.
He heard a strange noise and a door opened. "W-What the hell is this?!" Tears filled his eyes as tall alien creatures entered the room. His heart raced as the alien creatures, with their elongated heads and glowing eyes, stepped into the chamber. The man's mind raced with fear.
"P-Please, don't hurt me," he stammered, his voice shaking. The aliens approached him, and the man felt a cold metal object touch his groin. "N-No, don't touch there, please!" He pleaded, arching his back in vain attempts to move away from the intrusive device.
The alien's appendages, long and nimble, manipulated the machinery around him. The man felt a surge of warmth near his groin, and as he watched in disbelief, his cock started to swell and grow. "No, no, no!" he cried out, his voice strained as his dick grew before his eyes.
He bucked his hips, trying to escape the sensation, but the binds held him well. His thick cock lengthened, stretching the sensitive skin until it reached a foot in length. "WHAT THE HELL IS THIS??!!" He felt his cock grow girthier, until it was as thick as his thigh. Despite the size and weight, it stood erect and tall. He could see the veins bulging.
"A-ah, p-please, no more!" The man's eyes widened as his cock continued to grow, his mouth hanging open in disbelief. It reached about two feet long before it stopped.
The man's eyes darted around the chamber as his pulsating, throbbing cock continued to demand his attention. The aliens, unfazed by the man's pleas, moved on to the next stage of their experiment. A tentacle-like metallic appendage snaked its way toward his gaping urethra.
He screamed as it pushed in, stretching his cock even wider. It was the girth of a regular cock, the cock he used to have, and now it's fitting inside his new monstrous length. He moaned as it began to make small thrusts as it moved deeper and deeper.
"N-No! Uuuhhnnn....!! Not there! Haah, ahh..! S-Stop it!"
It went deeper and deeper, pushing past the now larger bundle of nerves deep inside and sending white hot sparks up his spine. He moaned, louder that he ever had having sex before, and he couldn't stop.
The 'tentacle' split up into three pieces. Two were quite small, delicately entering his seminal vesicles. He couldn't feel much of it compared to the remaining larger part.
The largest invader inched past his prostate, and the man let out a guttural moan as a wave of pleasure coursed through him.
The tentacle continued its journey, and the man felt it press against his bladder sphincter. It pushed through, and he continued to scream and moan incoherently. The large tentacle, now in his bladder, seemed to blow up like balloon, sealing his bladder. He didn't know yet that a liquid was starting to pump in.
His balls were now the center of attention. Another tentacle, thick and wide, wrapped itself around his right testicle, and another one did the same with the left. They started to squeeze gently, tugging on them lightly as if trying to milk a cow. "P-Please doooonnnn't!" he begged, his voice cracking as the pressure increased. He could feel something beginning to fill his testicles as they got tighter and heavier.
His testicles swelled, the skin stretching to accommodate the growing globes. They reached the size of two grapefruits rapidly. He panted, his breaths coming in ragged bursts. It felt amazing, all of this, but he didn't want this.
The man's body was now a playground for the alien's curious technology. As his testicles grew to the size of basketballs, he could no longer ignore the pleasure that came with this bizarre transformation. He lost track of time, of himself and the room around him, as they swelled as big as two beach balls stuffed into a tight sac. His veins were pronounced all over his balls, throbbing visibly. He looked like he was trying to cum but nothing was able to come out.
Finally, when his balls were like two boulders resting on the ground, he felt an orgasm overtake him.
The man's body convulsed, his throes of pleasure involuntary and intense. He screamed, unable to contain the wave of ecstasy that coursed through him, his cock jerking and twitching as if it were about to erupt.
But no cum came out. The alien technology had sealed his urethra, and it remained a tight tunnel, denying him release. He writhed, his face red and contorted, as the unyielding pleasure continued to build, his swollen balls now heavier than he ever thought possible.
Meanwhile, the tentacle still inside his bladder continued its work. The aliens had pumped a strange substance into his body, inflating his bladder more than he could ever imagine.
The man felt his stomach swell and distend. He could see his skin stretching taut over the rapidly expanding balloon that was his bladder. The sensation was indescribable, but it felt both wonderful and terrifying.
"N-No, no, p-please..." he moaned, crying and drooling through the tormenting pleasure. He had to pee so bad.
His pleas fell on deaf ears as the alien technology continued its work. A second tentacle entered his ass somewhere in the throes of everything else, and he finally began to notice it. He'd taken large cocks before, but this was so big it felt like it was the absolute limit. It started a lot smaller, slowly stretching him more and more until it was as big as it is now. It fucked him deep, adding excruciatingly pleasurable pressure on his abused prostate. It was so deep he could see it press his belly outward, fucking against his growing bladder and causing him to try to close his legs in a futile effort, feeling like his pee would burst out of his urethra any second.
The tentacle in his ass began filling his colon with the same substance that was inflating his bladder.
The man's belly swelled rapidly, bulging outwards as the alien substance filled his intestines. His skin stretched tight, the contours of his abs now a faint memory. The alien's technology relentlessly stimulated every inch of his inflating body.
"M-My stomach, it's... too much," he gasped, feeling the pressure building inside his belly. His once-sleek torso was now a bloated, distended mass, the evidence of the alien's experimentation writ large. He looked like he was overdue with triplets, and the swelling just kept going. Despite the liquid stretching him, his belly grew more like fat, soft and jiggly. He could hear the liquid slosh inside.
The aliens seemed to have no intention of letting him find any sort of relief. The tentacle inside his ass pumped more and more of the substance, pushing the limits of his intestines until his belly looked ready to burst. But it didn't. Something in this substance changed his body to be able to take this.
His cock, which had grown so thick and long, pulsed with every thrust from the tentacle inside his urethra. It felt like it was close to bursting with every pulse, the cum straining to be released. The man could feel the pressure building in his testicles, each pulsation of his engorged cock causing the heavy, swollen sacs to ache with pleasure. They throbbed as they were squeezed and tugged.
The man cried out as another dry orgasm overtook him. And another, and another, and another. He didn't know how long had passed since he gave in to the pleasure, his belly growing so massive he was pushed forward to lay on it, his ass in the air getting fucked, his cock and balls hanging over and being toyed with. He never noticed when he was freed from the bindings, his body now its own prison.
He tried to will his body to submit and just cum or piss or something, to allow the release that his body craved. But the alien technology was unyielding, as if mocking the captive earthling's desperate pleas. The alien tentacles continued their relentless work, teasing and fucking his cock, squeezing his testicles, fucking his ass, and filling his bladder and intestines.
The man's body, once toned and trim, was now a bloated mess of stretched skin and swollen balls. His cock, now a monstrous appendage, continued to throb, his urethra sealed as the alien device inside relentlessly pushed in and out, denying him the release he begged for.
His balls ached and throbbed in time with the thrusts of the alien tentacle that relentlessly fucked his urethra.
It felt good. He didn't want it to stop anymore, and it wasn't going to. He was happy like this, completely fucked and full and never allowed to feel the relief of release.
The aliens left him hooked to this machine from then on, its chemicals keeping him nourished. This would be his forever, never aging, never dying, never cumming or pissing or having any thoughts that aren't just pleasure. He would never know why this happened, or how he got here, and he would forget himself as he became nothing more than a stuffed and eternally fucked mass of euphoria.