"Would you rather be in a loving and sexual relationship with your mother or your father?"
"That's sick, Jon," exclaimed Karyn, through her shark teeth. "Are you really going to choose?" It was gross, but it was also kind of hot also. "And how would we be able to tell that something had changed?"
Jon blushed. "Yeah, I guess," he said. "I can always reverse it if I don't like it. I'm really digging these panties and I kind of want to sleep with my parents. And I'm not sure how we'd be able to tell unless we let it go on for a while. No harm in trying, though. I choose..."
