The Substitution Stone: Number

The stone glowed, but instead of granting the wish Jon had asked for, it changed the wish to "I wish that Karyn was *twins* and in my bedroom and desperately wanted to make love to me." In his room suddenly appeared two girls, both of whom looked like Karyn. They were identically clothed, but started to strip off their clothes. "What's going on?" asked Jon. "Karyn, why are there two of you?" "Karyn?" replied one. "You know me. I'm Kara." And the other added "And I'm Erin." Jon was confused. He had to admit he had a fantasy about twins at least once, but he certainly didn't wish for this. Something was seriously wrong.