The lab rat

by Beastly Muscle

A scientist makes a medical breakthrough with a newly-made drug that promotes muscle growth. As the drug is in its testing phase, the lab rat being experimented on gets a unique opportunity.

In the sterile confines of a modern laboratory, Dr. Ethan James, a brilliant scientist, embarked on a groundbreaking experiment. His subject: a humble lab rat named Squeaky. Dr. James’s goal was to test the efficacy of a newly developed muscle growth drug.

Meticulously, he administered a single pill to Squeaky each day, carefully monitoring its gradual effects. Days turned into weeks, and Squeaky’s physique underwent a remarkable transformation. With each passing dose, his biceps swelled like ripe melons, his pecs expanded into a formidable chest, and his quads and calves grew as thick as tree trunks.

But fate took an unexpected turn. One fateful afternoon, as Dr. James was momentarily absent from the lab, Squeaky’s keen senses detected the tantalizing scent of the remaining pills. Unable to resist the allure of further growth, he seized the opportunity and consumed them all.

Instantly, Squeaky’s body erupted in an explosion of muscle mass. His biceps began to bulge like cannons, his pecs exploded with size and threatened to burst through his skin. His quads and calves grew so immense that they resembled those of a behemoth. Even his glutes swelled to powerful proportions, becoming spheres of pure muscle the size of basketballs.

As the growth intensified, Squeaky’s manhood became engorged and throbbing. His testicles swelling to the size of grapefruits while his dick grew longer and thicker by the second. An overwhelming surge of horniness coursed through his veins, and he began admiring his newfound strength while massaging the head and shaft of his colossal dick. He came as he stroked his cock and ushered in another wave of growth.

Driven by the primal urge of new growth, he strained against the confines of his cage, his muscles rippling beneath his skin. With a deafening roar, Squeaky grabbed the bars of the cage and began pulling them apart, his muscles effortlessly shattered the steel bars of his prison. Freed from his captivity, he continued to grow exponentially, towering over the laboratory with his colossal frame.

He hungered for more growth and tore the lab apart looking for more of the growth pills. He could not find any more of the pills in his rampage and decided to await the scientist’s return, hopeful that he would bring more fuel for his growth. As he waited, his growth slowed and Squeaky settled into his new size. Hours passed as Squeaky explored his new body, feeling the heft of his pecs, the girth of his biceps, the roundness of his glutes, and the astonishing weight of his leaking cock. Squeaky soaked the floor of the lab in his precum while feeling himself up as he waited patiently for Dr. James’s return, hungry for that intoxicating feeling of growth.

Finally, the scientist entered the lab, his eyes wide with both awe and trepidation as he beheld the beast of pure muscle before him. Squeaky rushed to Dr. James, seizing him by the waist and lifting him effortlessly into the air. With a guttural growl, he pinned Dr. James down, his massive thighs crushing the man’s resistance. Dr. James attempted to struggle to escape the hulking beast pinning him down, but to no avail. There was no escape, and the scientist knew this, but despite how scared he was he still began to sport his own lustful erection.

Dr. James had left the lab to retrieve more of the pills, and Squeaky noticed when he smelled the scent of the drug in the scientist’s lab coat. Squeaky grabbed the bottle of pills out of the lab coat of the scientist as Dr. James stared at him awestruck. He secretly wanted this musclebound beast to blow up in size even more. Squeaky ripped open the top of the bottle and in one swift motion swallowed the entirety of the bottle’s contents. As Squeaky’s muscles flexed and bulged, his manhood grew erect to an astonishing size. He tore the pants off the scientist and thrust into Dr. James with animalistic force, his groans of pleasure echoing through the laboratory.

Hour after hour, Squeaky dominated the scientist, using his newfound power to fulfill his insatiable hunger for growth. With each thrust, his muscles grew larger and more powerful, until he had transformed into an unstoppable force of nature.

Finally, exhausted but triumphant, Squeaky released the scientist and watched as he collapsed to the floor in the puddles of cum from both of their emissions. As the adrenaline subsided, Squeaky realized the true extent of his power. He had not only broken the chains of his captivity but had also become an apex predator.

From that day forward, Squeaky roamed the world hungry for growth, his colossal physique a testament to the indomitable spirit that resided within him. And though Dr. James’s experiment had gone awry, Squeaky carried with him a legacy that would forever be etched in the annals of science.

Vote on this story

Call of the incubus by DaBook Recent college graduate Adrian Castille has started noticing cults rising up around his city. He investigates, following a cult to an abandoned warehouse, and witnesses a deadly ritual, and finds himself face-to-face with a powerful incubus. He stands his ground, telling the incubus he will be stronger than him. 9 parts 47k words (#93) Added May 2024 Updated 26 Apr 2025 25k views 5.0 stars (19 votes) No comments yet •Cock Growth•Cock Shrinking•Cock Theft•Huge Balls•Ball Growth•Huge Cock•Public Orgasm•Muscle Growth•Muscle/Strength•Muscle Worship•Man Scent•Pointy Ears•Butt Growth•Increased Libido•Getting Handsomer•Gradual Change•Transformation•Getting Taller•Plausible Size Difference•Size Increase•Hair Growth/Getting Hairy•Dom/Sub•Sex-Slave•Hyper Pheromones•Incubus/Succubus•Supernatural •M•M/M•M/M/M•M/F•M/Inh

One more drop by MegaMaker A college water polo player, Rain, is having trouble keeping up with expectations after a lackluster swim season. Afraid of getting cut from his team, he finds a mystery serum that improve his performance. To his surprise it works and his improved performance gets the approval of his entire team and his coach and really attracts the attention of his friend River. Will the attention go his head? Will his team and coach find out? And… will there be any side effects caused by the use of the serum? 16 parts 48k words (#89) Added Mar 2023 Updated 20 May 2023 85k views 4.9 stars (67 votes) No comments yet •Always Hard•Cock Growth•Huge Balls•Ball Growth•Huge Cock•Hyper Cock•Always Cumming•Hyper Cum•Public Orgasm•Multi-abs•Addiction•Straight to Gay•Hyper Muscle•Hyper Strength•Immobility•Muscle Growth•Muscle/Strength•Muscle Worship•Always Shirtless•Public Nudity•Man Scent•Butt Growth•Increased Libido•Gradual Change•Voice Deepening•Getting Taller•Forced Growth•Plausible Size Difference•Size Increase•Hair Growth/Getting Hairy•Lycra/Spandex•Complete •M/M

Freshman, fresh men by West Your best friend and secret crush is now your roommate during your freshman year of college. Both of your comfort levels with each other change when he emerges from the shower smelling fresher than ever, and also bigger each time. 7 parts 13k words Added Sep 2023 Updated 17 Feb 2024 30k views 4.8 stars (38 votes) No comments yet •Cock Growth•Huge Balls•Ball Growth•Huge Cock•Hyper Cock•Hyper Cum•Hyper Strength•Muscle Growth•Muscle/Strength•Always Shirtless•Butt Growth•Getting Taller•Size Increase•Retcon•Christmas•Valentine’s Day•Complete •M/M•M/M/M

The second subject by MegaMaker A college kid named Angel is kidnapped and brought to a facility to become the next test subject for underground scientific advancements. 14 parts 33k words Added Dec 2024 Updated 1 Feb 2025 24k views 4.6 stars (14 votes) No comments yet •Always Hard•Cock Growth•Cock Pumping•Huge Balls•Ball Growth•Huge Cock•Hyper Cock•Cum Milking•Always Cumming•Hyper Cum•Multi-abs•Other Mental Changes•Straight to Gay•Hyper Muscle•Pec Fucking•Hyper Strength•Immobility•Muscle Growth•Muscle/Strength•Muscle Worship•Always Shirtless•Man Scent•Butt Growth•Increased Libido•Foot Growth•Getting Handsomer•Gradual Change•Voice Deepening•Getting Taller•Giants•Forced Growth•Plausible Size Difference•Size Increase•Age Difference•Destruction/Violence•Blood•Nonconsensual change•Nonconsensual sex•Restraints•Lycra/Spandex•Hyper Pheromones•Horror•Complete •M•M/M

The real you 3 by MegaMaker For his second year of college Henry gets a new roommate named Roman. Things between them go well, but Roman seems to be hiding something. 3,116 words Added Sep 2024 9,158 views 2.0 stars (1 vote) No comments yet •Always Hard•Cock Growth•Huge Balls•Ball Growth•Huge Cock•Hyper Cock•Always Cumming•Hyper Cum•Public Orgasm•Multi-abs•Straight to Gay•Hyper Muscle•Pec Fucking•Hyper Strength•Immobility•Muscle Growth•Muscle/Strength•Muscle Worship•Always Shirtless•Public Nudity•Man Scent•Butt Growth•Increased Libido•Getting Handsomer•Voice Deepening•Getting Taller•Giants•Forced Growth•Plausible Size Difference•Size Decrease•Size Increase•Destruction/Violence•Nonconsensual change•Shapeshifting•Complete •M/M

Bull’s strength by muscl4life On a quiet farm far from anywhere, an orphan named Joshua grows up so huge and strong that he’s bullied for being a freak. His aunt and uncle raise him with love and teach him to accept who he is, but Joshua yearns to be among men who don’t just accept his giant body, but love and admire his amazing size and power. 28 parts 88k words (#36) Added Jul 2018 Updated 6 Oct 2018 109k views 4.8 stars (49 votes) No comments yet •Always Hard•Cock Growth•Huge Balls•Huge Cock•Hyper Cock•Multi-abs•Multicock•Muscle Growth•Muscle/Strength•Muscle Worship•Transformation•Getting Taller•Plausible Size Difference•Size Increase•Age Difference•Bestiality•Incest•Father/Son•Destruction/Violence•Infectious•Flying •M/M•M/M/M•M/M/M/...

The hidden truth by SomeMuscleGuy After confessing your feelings to your two friends, Isaac and Mark, they decide to share their biggest secret with you—and what better way to show you than to transform and grow before your very eyes? 2 parts 4,442 words Added Jun 2025 4,396 views 5.0 stars (3 votes) No comments yet •Cock Growth•Huge Balls•Ball Growth•Huge Cock•Hyper Cock•Hyper Cum•Public Orgasm•Hyper Muscle•Muscle Growth•Muscle Worship•Public Nudity•Pointy Ears•Butt Growth•Increased Libido•Transformation•Voice Deepening•Getting Taller•Giants•Size Increase•Human to Animal/Anthro•Dom/Sub•Infectious•Anthro/Furry•Werewolves •M/M/M

Three giant guys by MegaMaker Three short vignettes taking place in three separate universes, with three very hot growing guys.  3 parts 5,926 words Added Mar 2024 17k views 5.0 stars (7 votes) No comments yet •Always Hard•Cock Growth•Huge Balls•Ball Growth•Huge Cock•Hyper Cock•Self-suck•Always Cumming•Hyper Cum•Public Orgasm•Multi-abs•Addiction•Getting Dumber•Hyper Muscle•Hyper Strength•Immobility•Muscle Growth•Muscle/Strength•Muscle Worship•Public Nudity•Man Scent•Butt Growth•Increased Libido•Gradual Change•Voice Deepening•Getting Taller•Giants•Forced Growth•Plausible Size Difference•Size Increase•Hair Growth/Getting Hairy•Destruction/Violence•Hyper Pheromones•Shapeshifting •M