After the room was empty except for them, Ty noticed someone else walking towards the locker room. It was Matt, a tall, skinny 16 year old, who was very shy and very smart. With him was his girlfriend Cynthia. They had an early dismissal from school, so Matt was going to get changed. Looking inside, Matt found the room empty (or so he thought), and headed over to his locker.
Taking off his gym shorts, he felt a tingling within his boxers, causing him to get an erection. He had a healthy 6 inch long cock, but now he saw it was starting to get longer! Shocked, Matt just stared at the growing tent in his underwear. Reaching 9 inches long, Matt's cock started to pull the waistband of his boxers away from him. Soon it reached 10 inches long; Matt tried to push down into his boxers but it just ended up coming out the end of his underwear, and then poking up, revealing its large size. It was now over a foot long, and four inches thick. Matt pulled up his gym shorts, but the now 14 inch long monster made an extremely obvious bulge.
Matt tried to readjust it, but he ended up taking his pants down again, unknowingly triggering even more growth. Setting it back into its original position, Matt's now 16 inch cock was starting to cause his boxers to tear. Matt didn't notice, but he had actually grown taller, and was around 6'6", and had a fair amount of muscle. Dismayed that it was still growing, Matt tried putting his gym shorts back on, succeeding this time, as his foot and a half long schlong was causing his boxers to tear even more. Pulling his shirt up, he attempted to put his cock underneath his shirt, but as it was now 20 inches long, it was getting difficult. Even when pressed up against his chest, his cock was 7 inches thick, making it quite easy to tell what he was hiding in there. Soon the growth slowed down to 26 inches long, almost two feet longer than what he woke up with. His shirt was tearing slightly at the front, due to his increased height (now 7 feet tall) and his increased muscle, as well as the fact that there was an 8 inch thick cock there; due to the amount the shirt was stretched, the tip of the head of Matt's cock was actually poking out some.
Matt decided to walk out and tell his girlfriend what happened.
Cynthia looked at him lustfully, but then gave him a choice.
"Well, you certainly can't go around looking like that. You can try changing back into something else, or I'll go change myself." Cynthia said.
Ty smirked as he thought of the possibilities.