"Unnnngh...I-I feel...ugh!" Charlie’s body began to grow stronger all around, the boy's muscles finally getting definition. Having only ingested a small fraction of the Muscle Tech-X, he would only gain strength, enough to become an athletic kid fit for sports.
Vanessa and Tony watched as the boy grew decently large biceps, his forearms thickening and his shoulders getting broader, his upper arms filling up his short sleeves for a comfortably snug look. It continued into the rest of his shirt as his chest pushed out into a pair of fledgling pecs that filled out the front of his shirt, the bottom of it hanging in front of his new four pack of abs, not very defined but pretty firm to the touch.
"Ugh...hah...hnnngh..." Charlie's high preteen voice started lowering a bit with the bass-y tones of a young freshman jock as his neck thickened, his little Adam's Apple starting to protrude a bit more as his legs thickened with bulk, his calves growing stronger and his thighs especially getting meatier. The two of them were in awe watching the young teen grow bigger and stronger in front of them.
In fact, Charlie didn't just get bigger in terms of muscle. His body started to catch up in height too. The boy grunted and panted as he grew taller, his short 5'0" body finally growing to the proper height of a boy his age, stretching up to 5'7", a bit taller than Vanessa, but expected for a fourteen year old.
With a flushed heat in his face, his body sweating from the collective body heat of the party crowd coupled with the heat of the growth and producing a body odor he had only just started making in the last year or so, Charlie groaned as he felt his cock getting bigger in his shorts, his package starting to bulge out a bit as his ass followed suit to fill the back. He bit his lip as he could feel his feet getting bigger, the teen’s shoes bulging a bit outward for an awkwardly tight feeling. As his youthful face lost some of it's baby fat and no longer looking younger than he was, the boy could feel a new release of testosterone flooding his system and being at the starting line of puberty as he was, it was a rush that made the horny feelings he only just started to grasp intensify, causing his decent five inch cock to harden into a round lump in his shorts that was trying to break free. Some hairs started to grow in on his legs, the little bush beneath his underwear growing up and out towards his bellybutton.
Vanessa could only feel flustered from seeing her not so little nephew now looking like a proper healthy fourteen year old, the boy now a cute young jock with a strong body fit for the football field, which wasn't super jacked but was about as big and strong as a boy his age could naturally be. His body may not have the capability to contain true power, but he certainly looked like he had the potential to be a real strong man when he grew up.
Charlie breathed slowly as he looked down to see how big he'd gotten. His clothing was now not as fitting as it used to be, though it still fit him enough to contain his muscles and not rip open. His growth in height made them ill-fitting in a length aspect, his shirt unable to cover his torso completely, giving a little teasing view of his lightly defined v-shaped waist. His shorts were unable to reach his knees, being filled by his thick thighs capable of running across the field during a game. His shoes were bulged out and very close to bursting, but they stayed intact, his bigger toes stretching out the fabric as he moved them.
"Uhhh...is it over?" Charlie held his head feeling a bit foggy in his mind. He started remembering joining the lower leagues of football teams in middle school, on his way to getting into junior varsity as a highschool freshman. Resting against a counter, he looked around to see his aunt and a friend of hers staring at him in shock. He spoke to Tony in his new teen kid voice. "...What? Is there something on my face, bro? Mmfff, fuck, my clothes are so tight..." He stretched out his midsized body, giving everyone a glimpse of his bellybutton as he casually walked around, his sexually budding figure catching the eyes of a few girls at the party. He cocked his head in a jockish greeting of acknowledgement as they smiled and walked past him, the young teen smirking. It would seem his mind had changed a bit, becoming more confident and outgoing. The eager boy wanted to flirt with them so bad, feeling an awkward kind of attraction that most would find cute since he's at that age where one might get curious about love and sex.
"Damn...I didn't think this thing could effect kids too." Tony said in astonishment. Vanessa looked at the drink she could've had by now and turned to Tony. "What the hell is in this stuff? I thought it was just some protein shake or something!" Vincent chimed in. "Nah, it's Muscle Tech-X! If you drink it, you get huge muscles like me. I did it, and now look at me!" He flexed his strangely defined body. "In fact, I think I kinda want another can." He chuckled.
Charlie looked interested when he said that. "Oh, sweet! Get me some too, bro!" Vanessa grabbed him by the shoulder, feeling how much broader it's become. "Ohhh no you don't! It's nice you're looking healthier than you've ever been, but I'm not letting you turn yourself into a meat head like him." Charlie looked at his aunt glaring at him, returning with a soft smile. "Aww, c'mon, Vanessa! I wanna try it and see if I get big! Please?" It would seem he had only a faint memory of what just happened, thinking he'd always been a jock. He looked back at the girls hanging out with the other college dudes, and wondered if he'd be able to pick up a date. Though, a nagging feeling inside of him wanted him to drink more of the Muscle Tech-X. The idea of getting laid at a college party made his heart flutter with excitement, and his cock pulse.
Tony and Vanessa looked to each other. "Well...he certainly is a growing kid now..." He joked nervously. Vanessa just rolled her eyes.
But they couldn't leave Charlie like this. Not in a house full of party goers. What were they gonna do?