Adam watched in amazement as his dad flashes him a toothy, wolfish smile, almost seductively. The big man turned his back to his son and watched the huge men on the television move between poses, copying them in all their splendor. The announcer called the next pose, a side chest. Adam gulped and moved further to the side, getting a view of his dad's insanely built, carved and massive back. He could tell that his dad would fit right in with the mass monsters on the screen. He touched himself as he looked at his dad's reflection on the TV, the huge man grinning wildly to himself, the now strained pair of briefs distended with his huge, blood-filled equipment.
Adam's breath was nearly taken away as the announcer calls for the gentlemen to turn around and hit a back bicep pose. Adam's dad mirrored the men on the screen -- which meant he was now facing his gobsmacked son. Adam stepped back and had to hold onto the kitchen counter as he came in his pants. His dad was relishing in the moment as he forced all that blood into his huge arms, easily 22" around and hard like diamonds, veins hissing along the surface, feeding more and more energy into his pose. But as much as his dad was forcing blood into arms, even more was forced into his junk. His father was packing at least 8" of heat, and he was only semi-chubbed.
"Huff, huff, hooo boy, flexing's hard work," Adam's dad grunted as he dropped the pose. The beast of a man already had a thin veneer of sweat that covered his muscled frame, glistening off the fine dusting of body hair that covered his body. He sauntered forward, closing in on Adam. The huge man grunted when he felt his massive goose egg sized testes rolling over his thighs. He reached down to adjust himself when his hand brushed against his even more massive erection, the thick head of his cock stretching out his briefs to the point of breaking at least 10" from the base of his pelvis.
"Aw jeez," the teen's dad guffawed, a huge blush crossing his cheeks. "Sorry, son. I don't know what came over me!" he chuckled lightly, trying in vain to cover his prodigious tool. Adam just couldn't take his eyes away from it.
The bodybuilding father strutted over to the fridge, making sure the door covered his junk so that his son wouldn't be 'burdened' with the sight of indecency. If only he knew... He took out a pitcher of water, still turning to the side to try to hide the excitement of his newfound size and strength. Only... when he closed the door, Adam got a sight of all it's thick massiveness in profile view, the big dad's cock sticking out obscenely, his giant pecs trying to do the same.
"Ah, you got more of that sports drink!" Adam's dad exclaimed, pointing at the now full flask Adam was holding. The skinny teen didn't have time to retort before his hungry father took it and greedily began to guzzle down the fluid, giving off a satisfied grunt as his wiped the fluid from his lips, the magic potion downed in seconds. "Mmph, that hit the spot! God, that stuff tastes awesome, you gotta tell me where to get more of it, boy!"
In the meanwhile, the next line up of bodybuilders had come up on stage and Adam's dad was intent on getting back to flexing with them. Adam's dad turns to the screen and throws his arms up and flexes, his biceps exploding in size.
"Man, in just a few weeks, I've gotten this far, imagine what I'll look like in a couple more?" Adam's dad boomed proudly. Unbeknownst to the two of them, the potion was doing its work, turning the bodybuilder-sized muscleman's imagined body into his reality. Adam was about to find out just how big his dad had envisioned himself.
The announcer calls for a lat spread and Adam is floored as his dad copies the pose, his lats flaring obscenely. Even from his new vantage point, Adam had to move even further to the side to see the TV, his dad's muscular back completely swallowing up space. His dad's grunts and huffs grew deeper as he got thicker and wider, his muscles bloating with more size and power.
"Grrr," the dad snarled as he hit pose after pose, his muscles growing with each one. Perspiration dripped onto the hardwood floor underneath him, beads of sweat rolling off his titanic arms. He even groaned as the sweat pools and dripped off his thick, silver-dollar sized nipples.
"Yeah, more. More, monster mass!" Adam's dad boomed as he turned to Adam. The teenager gulped as he watched his dad begin to grow even more. This time, his dad moaned lowly as his bones snapped, his skeleton reconfiguring as he began to inch taller, from average height to towering over Adam, easily 6'6". The kid mewled as he watched hairs sprouting out of his dad's face, his brows furrowing to become more severe, more masculine, an idealized vision of what his father should be. What was once a patchy 'stache and beard, now was a full, luscious one. Hell, Adam watched as his dad's hairline grew back in.
"Whew," Adam's dad huffed, relaxing his stance and standing up straight. He was simply titanic now, even scaled down to average height, he'd be half again as wide as the best of the best on the TV, the beast at least 500-600 pounds of prime muscled beef. His titanic thighs and ass muscles took up more space than ever before, between them and the now even greater junk in his basket, his briefs gave up the ghost.
The now titan of a father's briefs split in half, failing catastrophically. The dad hollered as his giant 15" cock broke free of its cotton prison, spilling out, his avocado sized balls jostling as they slapped lewdly against his giant thighs. The front half of the briefs flew forward, hitting Adam in the face with enough force to knock the teen off his feet.
The teenager careened into the counter where the flask had been placed back down. Adam slumped to the floor, dazed. The flask tipped over, having magically been filled to the brim once more as it had completed his dad's transformation once again. The potion spilled out, a splash of it landing in Adam's mouth.
The last thing Adam was thinking about...