Ty looked around and spotted a small boy, who he estimated couldn't be older than 11. The boy looked slightly sad, and stared forlornly at the exercise equipment. Reading his mind, Ty found that the boy was named Jake, and was actually 13. Jake hadn't hit puberty yet unlike a lot of his classmates, and was feeling understandably a little left out. A lot of the boys were picking on him. Ty was saddened by this and decided to make things right. He decided to give Jake a head start on puberty.
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Jake stared at the equipment. Apparently he was too small to actually use it, according to the gym employees. He sighed, then got up to leave the gym. However, as he passed a height measurement arm attached to the wall above his head, Jake stopped and felt a tingling sensation run through his whole body.
At first nothing occurred beyond that. Then Jake felt his shorts start to feel tighter. He looked down, and was surprised to see a faint outline of his cock where there hadn't been before. But that couldn't be right, could it? Jake knew his cock was only 3 inches, but the outline looked to be more than double that. Not only that, it was becoming more defined by the second, and also strangely appeared to be growing. Jake groaned. His shorts felt really tight now! Finally, just when Jake's shorts felt like they were going to burst, the pressure stopped increasing. Taking a look, Jake gasped. There was a clear outline of an enormous cock traveling partly down his left leg. Just below the tubular bulge were two more bulges that resembled testicles. Only these were much bigger than Jake's previous equipment. Jake estimated them to be softball size.
Jake wondered... the bulge ended just above the end of the leg of his shorts. If he reached down, he could probably see what was causing the bulge, just to make sure it wasn't a dream. As he bent down, he felt another tingle go through his body, but he was much too excited to care. Reaching his hand inside his leg, he grabbed the bulge. The effect was immediate: Jake moaned in pleasure, and he began to feel a sensation he had never felt before. He could feel his cock harden, but he didn't want to be hard here, not now! Jake stood up to avoid looking at the bulge, trying to distract himself.
Suddenly, Jake whacked his head on the height measurement arm. But that couldn't be right, when he had first stood there the arm had been much too high for him to hit. But now, as Jake looked again, he was now eye level with the arm... no wait, he was still growing! Jake stared in amazement as his eyes slowly moved upwards past the arm. Finally the movement stopped when the arm was at his shoulder level. Jake glanced at the number, which read 70 inches. Gaping, Jake carefully moved the arm up over his head, then brought it down to his head. Stepping back and reading the number again, Jake's mouth dropped open. The number read 76 inches. 6'4, a full 16 inches taller than before!
As this dawned on him, Jake realized several things at once. The main one was that his clothes had not grown with him. His shirt had ripped in several places and was riding almost a foot higher than his waist, clearly meant for someone much shorter and smaller than him. His shorts were almost like underwear at his new size, and his shoes had actually burst open as his feet had outgrown them during his growth. Jake had to find somewhere private, fast. He spotted the gym bathroom and quickly rushed inside, before catching a glimpse of himself in the mirror.
Above his neck, Jake's face and head looked exactly the same: boyish features, boyish hairstyle, and almost no sign of puberty or maturation. Below his neck though, Jake looked completely different, no longer the skinny short boy that he had been earlier. Jake's body had gained a lot of height, but also some width. Jake wasn't muscular by any means, but he didn't look so skinny anymore. His shoulders were much wider in comparison, and his feet were also awkwardly big, even considering his new height. Jake's body had also gone through some puberty, though not much. Jake now had pit and pubic hair.
Speaking of the pubic region... Jake pulled back his shorts and briefs and took a good look. Jake's tiny cock and grape-size balls from the morning were gone. Instead, a enormous (Jake estimated a foot long) and soft cock hung down between his legs, accompanied by a pair of baseball-size testicles. Jake was in awe of his equipment. It easily dwarfed almost every other male, let alone other boys his age.
Jake was so incredibly happy. He had wanted to grow bigger than everyone else, and his wish was now granted! But how would he get out of the locker room?