In the SUV, Cody and Jim climbed in the back. The evil brother and friends sat in the middle seats while the mother drove.
Cody and Jim were giggling. Jim kept grabbing Cody's upper arms, chest, thighs, even his lats.
"Quit it beanpole!' said Cody, "You're making me get excited!"
Sure enough, there was a 5 inch long boner stretched out against Cody's tropical boardshorts.
Jim giggled. "Beanpole?"
He slipped the balloon in his mouth when Cody looked out the window, an whispered, "control Cody's size!"
He quickly blew a big breath of air into the balloon, then turned with his arm hanging over the back seat into the storage area, hiding the balloon from Cody's view.
Cody immediately felt something, as another 10 lbs of muscle descended not his 5'2" frame. But when he turned to look, all he saw was Jim looking out the window, with the drawstring bag around his neck.
Wonderingly, Cody felt his thickened chest and upper arms and his thighs, now defined with teardrops. He was really muscular for his age and height, like a 16 year old gymnast instead of a 12 year old boy!
But Jim just played dumb. "Good thing I didn't grow you any bigger, you wouldn't be able to stop touching yourself!"
Cody blushed. Jim suddenly gaped. Cody had a 7" boner in his pants. He'd said bigger in his wish, not muscle. So Cody was getting both muscle and a bigger penis and probably taller too.
Just then Cody leaned forward to argue with his brother. Jim saw Cody's back defined, with his lats pushing out against his t shirt. He quickly turned his head, lifted his arm and blew a long breath into the balloon, making it swell considerably from the lung full of air. Cody couldn't hear the air because of the radio and the noise of the car driving, but Jim saw Cody's lats swell prodigiously out against his t shirt, and his torso elongated about 3 inches, as did his legs, and his deltoids swelled against the t shirt. Even from the back angle Jim could see Cody's peeks swell heavy and push outward. The t shirt pulled up out of the waistband of the boardshorts.
Cody paused, then sat halfway back, and grabbed his now softball sized bicep in wonder.
"Jim!" Cody whispered. "I think I'm still getting more muscular!!"
Jim just looked innocent and shrugged. He shook his head no. "You're just getting used to it!" he told Cody.
Cody turned back to argue about the radio station, and as he twisted Jim saw a now 9" python pressing against the crotch of the Cody's shorts, as well as a significant bulge from his now freakish testicles. It was amazing, seeing Cody at 12 years of age with the maturity of a porn star and the muscles of a gifted bodybuilder.
A bodybuilder. Jim liked that thought and quickly blew two more giant breaths into the balloon, and Cody winced as he felt his muscles grow even bigger, his legs longer, his butt more muscular under him as he sat there, and the t shirt was now very very tight across Cody's lats and pectorals and traps and deltoids. He was freaky big now, especially for his size. And speaking of size, his cock was swollen gross big and wrapped around his hip under the board shorts. It must be almost 11" now!
Jim grinned. Cody shifted to get comfortable, but was so interested in the radio argument he didn't even notice his giant increase. So Jim did what any 12 year old would do. He blew two more giant breaths into the balloon, whispered "release" and deflated the balloon. He barely tucked it away when Cody grunted at the sudden increase. Now his t shirt only reached his midriff, and was stretched and a bit torn across Cody's magnificent lats. His cock was now easily over 13" long.
He sat back, astounded at his new size, and held up his arm and flexed. A soccer ball sized bicep swelled tremendously. He placed his hand over it, feeling the power. "Amazing!" said Cody. Then he looked down and saw his huge cock. And gulped. He quickly scooted from the car and ran upstairs. Jim followed. Cody was now 5'11" tall, 4 inches taller than Jim. Huge for a 12 year old!!