An Incest Card

"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..."