"I think," said Jon, "that Karyn doesn't know how to make wishes. The way she said that, the first one of us to take off his own disguise triggers it. So why don't we take off each other's disguises? Neither one of us would be taking off his own disguise. So it wouldn't do anything."
"Hmm," said Alan. "But I don't know how to take off nails or polish." Unknown to them, Karyn had wished that they don't know how to take those off.
"You know what?" said Jon. "I don't know, either. But there's got to be someone we can ask."
Some time later, they had indeed managed to take off each other's disguises, except for the nails and polish; they had gotten help from someone at a beauty supply store to tell them how. They didn't seem to be transforming.
"Wait a minute," said Karyn. "I just realized. I left a way out. If they take off each other's disguises instead of their own, nothing will happen. Ah, well. It's not as if we don't have unlimited wishes. Here's another one. I wish..."