(older brother's POV)
Liam couldn't wait to start the baseball season! After his summer growth spurt, he was now tall enough to really be a powerhouse player on the team. Liam knew because he had obsessively measured over the summer. After finally reaching 5'4", Liam decided it was time to sign up. He was really happy that the first practice was just next week.
As a tingle ran through his cock, Liam was jerked out of his daydream and reminded of why he came to the clothing store. He needed a baseball uniform, baseball cleats and a baseball cup to protect his manhood. Or boyhood, he sullenly reminded himself. But maybe he could a slightly bigger cup than he really needed and make it appear he had a bigger tool. Liam began to browse the cups.
As he browsed, Liam felt his cock begin to press against the material of his baseball uniform, throbbing harder and harder. He fantasized more about the cups. He had just started to watch porn on the internet, and although most boys at school talked about breasts and vaginas, Liam often found himself looking more at guys - their cocks and their muscles. He strongly suspected he was gay, but didn't really care.
Liam continued to fantasize. In his daydream, he could feel his cock expand. He dreamt about having a big cock, what it would be like to not fit it into his pants. He imagined his cock growing, becoming a thick meaty tube jutting out from his groin. He wished for a big cock, just to feel what it was like. He imagined the heavy weight of a long swinging dong from his crotch, coupled with two big balls.
Liam was snapped out of his dream and back to the present suddenly as he realized he was making moaning sounds out loud. He blushed and continued to browse the cup rack. Without looking down, he noted that his cock was still extremely hard from his daydream, though something seemed off today.
"Eh, why not. I can always put it back right?" Liam reasoned with himself as he pulled an XL cup off the rack. The packaging noted "Meant for big men with big dreams!". Liam snorted, then pulled the cup out of the box and looked down to try it on, but then he blinked. Maybe he had arranged his cock differently inside his shorts this morning? Did he wear a new brand of underwear? Did he accidentally put a cup down his shorts already while he was daydreaming? Liam wasn't sure, but he knew that the bulge in his shorts was much bigger than usual.
Sitting down on a nearby bench and bending over, Liam took stock of the scene. Liam's shorts previously had been almost flat, with no real discernable bulge. Liam knew that his hard cock reached only around 4 inches, and also knew from experience that it created a small hump in his shorts, nothing more. But this was different.
In between Liam's legs were two circular bulges, each of which was about the size of a tennis ball, maybe slightly more. Just above that, the outline of a large tube was clearly visible. It snaked around the two other bulges and ran a few inches down Liam's left leg before flaring out in a large mushroom-shaped cockhead. Liam snorted. "If this is what they make cups look like now, this is ridiculous. I need a size smaller". He reached into his shorts to pull it out and touched... skin. Confused, he reached again, and found nothing.
Even more curious now, Liam dashed to the nearest dressing room. On the way, he could feel a heavy swinging weight in his shorts. He ran in, closed the door, and pulled off his shorts as quickly as possible. No cup was inside the shorts. Liam turned towards the full body mirror and gasped.
The boy that stared back from the mirror looked like Liam. Like, but not exactly. For one, Liam was pretty sure he didn't own a monster cock like this one. He stared at it blankly for a minute, his mind not processing that his incredible dream had become reality. Turning to the side, he continued to examine the amazing python for a minute, before he grabbed a measuring tape.
Giddy with glee, Liam found that he was now the proud owner of an 11 inch cobra, thick as a can of Coke and complete with a set of nuts the size of tennis balls. He couldn't even process the amazement.
As if on cue, Liam felt his new cock jerk a bit, then begin to rise. The cobra began to fill with blood, becoming hard and extending longer and longer. Finally it stood straight up, daring Liam to take it for a test drive. And test he did. Liam began to jerk off, at first slow but gradually speeding up. With how sensitive his new cock was, it didn't take long for Liam to shoot his load. He shot out a rope of cum with a cry of ecstasy, and collapsed on the floor for a few minutes afterward, still recovering from the pleasure.
When he could finally stand again, Liam's cock was already hard, but he did not dare jerk it again. Measuring once more, he found it to be 12.4... no 12.5 inches long fully erect. Over a foot long! Liam was so confused how this had happened, but he didn't care. All he knew was that he was really happy. He managed to put his clothes back on, noting the still-ridiculous bulge in his shorts, and left to go home.