Jon reached into the hat, and pulled out three slips of paper. The first one said "genitals".
The next two slips said "erection" and "shrink".
Before he could say anything, Jon started to feel incredibly aroused. He felt his cock start to harden, and he tried to cover his crotch.
"No fair!" said Karyn, feeling embarrassed about Jon seeing her completely naked, double her usual size, with large nipple-cocks on her huge breasts, "you have to let me see!"
Karyn, now a lot stronger than Jon, easily pulled his hands to the side and yanked his pants down. Karyn watched in fascination, and Jon watched in embarrassment, as his penis quickly grew hard and erect.
Only, instead of growing, it was shrinking. Jon was soon sporting a 1-inch erection which was almost invisible in his tangle of pubic hair. His scrotum looked like a shrunken walnut with pea-sized balls inside.
Karyn giggled. "You're looking a little under-endowed there, Jon. OK, now let's figure out a way to change back."
Jon was bright red with embarrassment. The worst part was that he was so horny that he wanted nothing more than to fuck Karyn right that moment - but with his tiny dick and her giant vagina, he knew that it wouldn't work.
Jon picked up the stone and said "I wish Karyn and I were back to normal!"
Nothing happened.
"Oh no!" said Jon, "I wished that the changes would last for a week, so the stone can't undo them until the week is past!"
