Climbing into the SUV, Cody's mom didn't seem to notice Cody's new muscles. Cody and Jim just sat in the back of the car, and they started the drive to Cody's house.
Getting out of the car, Cody and Jim high-tailed it up to his room, barely managing to say thank you to his mom for the ride. Shutting the door and locking it, Cody immediately turned to Jim. "So what do you want to do with it now?" he asked excitedly.
Jim thought about it. "Well, we've already grown your muscles right? What about..." he lowered his voice so that Cody's mom wouldn't hear, "your penis?". Cody nodded excitedly and hurriedly pulled off his shorts and underwear. His modest 3 inch soft cock hung out.
"Control Cody's cock size" Jim said to the balloon. He took a last look at Cody's softie before blowing into the balloon. Cody felt an odd tugging at his cock. He realized it was because his cock was growing bigger and therefore heavier! Both boys looked down in amazement as Cody's cock and balls inflated with size and weight. In a moment, his soft cock was growing past 5 inches in length. Cody now had a bigger than average cock especially for a young teen.
Jim blew quickly again into the balloon. In just a few seconds Cody's cock grew bigger and bigger, until it was over 8" in length. His balls were now almost the size of tennis balls!
"That's so big!" Cody exclaimed, "can I have a turn now?". Jim shook his head and blew again into the balloon. Once again Cody felt his cock swelling up as it grew to 11 inches long, the biggest cock Cody had ever seen! "Ohhhh man!" Cody moaned and stroked his huge genitals. Jim startled to giggle and almost let go of the balloon, but stopped himself just in time. He gasped "Release!" and let the balloon deflate.
Both Jim and Cody stared at Cody's new massive endowment. "Holy shit! Will it fit into your underwear?" Jim asked in awe. "I don't know... let me try!" Cody said and he pulled his underwear up. After a lot of tugging and packing he managed to fit his endowment in his underwear, but it hurt a lot and the bulge was ridiculous. It looked like Cody had stuffed a basketball into his underwear. Pulling his stretchy shorts over his bulge didn't help either.
Trying something new, Cody fed his cock through the leg hole of his underwear. It made things significantly less cramped (though still tight) in his underwear, but of course the bulge now clearly showed Cody's cock running down his leg. Jim just stared all the while.
"Can I try the balloon now?" Cody asked. Jim...