"Now that I think of it," said Karyn, "it shouldn't be too hard to fix. You said you wanted to become human. Well, all we have to do is use the stone to wish us separate, because when we're separate we'll still be human, right?"
"I see. The wishes that give wrong results are the easiest ones to fix. Because the right result is still consistent with the wording of the wish, so we can just directly wish to fix it."
"Okay" said Karyn. "But I have to go to the bathroom..."
Jon didn't particularly want to know how it feels having the other person in a shared body use the bathroom, and made the wish. "I wish that me and Karyn were two separate people, who each have all the parts of a normal human. I also wish we're dressed."