Ty let out a loud moan as he felt Nick's 11.5 inches slide into him. The extra two inches made a ton of difference, filling Ty up even more than before, making him shriek with pleasure. Nick worked Ty over with slow but strong thrusts, driving his cock in deep, using his new muscles to pump it home slow and hard.
Ty groped Nick's strong shoulders, feeling the tensed deltoids under the pale skin. He ran his hands up Nick's traps and caressed his neck, feeling how studly he had made his formerly-skinny friend. His hands slowly moved down Nick's chest, feeling the firm pecs that had grown on the once-bony expanse.
Ty wanted more. He concentrated on making that happen.
Nick grunted in surprise as he felt his muscles tingle and twitch, then start to grow in spurts, each beat of his heart making them spasm and bloat. His body lengthened as he grew up to six feet, three inches tall. Muscle rushed to fill Nick's newly-expanded frame, and in moments he looked like a junior bodybuilder, then like a middleweight.
"H-how big are you making me?" Nick asked between pants, as he slammed his cock into Ty with increasing force.
Ty caressed Nick's strong chest, squeezing the hard nipples. "How big do you want to be?" he asked.
"Aww fuck..." Nick replied. He had never imagined he would be so big! But the bigger he got, the more he realized that he liked it! "Make me huge, Ty!" he demanded, "A real monster!"
Ty was only too happy to comply. He made Nick three inches taller, bringing him up to six and a half feet tall. Every muscle bloated magnificently as it swelled with new size and power, as Nick grew to a size that would make most superheavyweight bodybuilders green with envy. By the time Ty was done growing him, Nick was over 400 pounds of rock solid muscle. He roared as he slammed his dick into Ty's new pussy, loving the feeling of the tight hole around his big dick, loving how huge and strong he was, loving the feeling of Ty's girly little hands as his smaller friend caressed and explored his huge muscles. To finish off the transformation, Ty grew Nick's erect dick to 13 insane inches, and tripled the size of his testicles.
Nick felt the surge of testosterone hit him. He roared in rage as he brutally fucked Ty, using his giant body to slam his oversized cock home hard and fast while Ty cried out in ecstasy. Ty began to wonder if he had gone overboard; his friend was so big now, Ty was worried that he might be damaged by the giant tool that was ravaging his pussy, or just by Nick's seemingly-skyhigh strength levels. But Ty couldn't deny that he was incredibly turned on by Nick's new physique, nor could he deny that the excitement and pleasure from being fucked by the big man eclipsed any worries he had. The hulking brute began to grunt, his thrusts becoming short but hard and deep. Nick's huge body trembled, and he thrust violently into Ty, every massive muscle tensing up suddenly as he came, his giant dick spasming wildly as it pumped Ty full of the muscleman's big load.