She couldn't believe there had been a loophole in her plan. Oh well, fixed easily enough -- she just had to be a bit more precise. While she was at it, though, she figured she may as well have a bit more fun with it. After all, just having his cock grow indiscriminately would only be fun for so long. May as well prolong the fun (and humiliation) as much as possible.
"I wish Carl's cock would grow... a quarter inch every time he looks at a girl's breasts," Joelle whispered to herself. When they were dating, she had caught him snatching furtive glances at other girls chests at least a few times a day.
Predictably, within seconds Carl glanced over at a pair of tits to his left that belonged to a girl named Tiffany. Instantly, his cock grew a quarter of an inch. He barely noticed this small change, but Joelle knew quarter inches upon quarter inches would rapidly add up.
She decided to raise the stakes a bit, though, just for fun.
"I wish all of the boys in the class other than Carl would be replaced with hot, busty girls," whispered Joelle. "Aaand, I also wish that this would not seem odd to anyone. Except Carl." Immediately, twelve seats that had previously been occupied by guys now held gorgeous women wearing tight shirts that barely concealed the shapes of twenty-four C and D cup breasts.
The disappearance of all the other guys seemed quite odd to Carl, but given the previous night's events, he wasn't that surprised. Funny, he thought to himself, first I could make my cock grow by setting my watch, and now I'm the only guy in a class full of total babes! Not a bad twenty-four hours!
Joelle knew otherwise, of course. She sat back smugly as Carl surveyed the scene, and his cock grew 4 or 5 more inches. Soon it would be out of control! What's more, through no doing of her own, it was becoming visibly erect underneath his slacks. She imagined what would happen when the pressure against his pants was too great, and giggled inwardly.
Sure enough, a few breasts later, Carl's erect cock burst forth from his pants, in full view of 21 gorgeous women. The ripping noise of his pants drew the attention of every one. Reactions were mixed. Some blushed and hid their eyes, others just gasped, still others giggled uncontrollably. Carl's embarrassment was apparent.
"Let's see," thought Joelle. "How can I make this a bit more humiliating for him?"