Jon's idea...

Jon straightened up and cleared her throat. "I wish," she said, grasping the stone tightly, "that Karyn and I would become angels, defined as the popular conception of the same, except that we will definitely be physical creatures and have free will, and that this wish will be in effect until we both decide it to be cancelled."
Both girls felt a sudden tingling along their shoulder blades as Karyn's shorter hair grew down to shoulder-length. The tingling intensified and soft, feathery wings burst out of the backs of their shirts, ripping through the shirts and their bra straps, leaving them with nothing on above the waist. Their wings spread out to about a ten-foot span. Jon's feathers were a very light gray, while Karyn's were pure white. Halos of soft yellow light, about what one might see from a forty-watt bulb, formed over both their heads. The tingling subsided and the change was finished.
Jon and Karyn looked at each other. "Um," said Jon, "maybe we ought to fix the clothing thing."
"Right," Karyn said. They pulled off their jeans and Jon grabbed the rock again. "I wish," she said, "that we were wearing outfits that were designed around our wings, and that our wardrobes were designed around them until we cancel the original 'angel' wish."
Both girls blinked and suddenly they were attired in long white dresses with slits along their shoulderblades, and their missing bras had been replaced with ones that hooked above and underneath the bases of their wings. A quick look in Jon's dresser confirmed that the rest of their clothes had been fixed.
Jon and Karyn looked at each other for a minute.
"Well," said Jon, "what do we do now?"