Pete suggests

"Just wish to be a girl for the next day," said Pete. Jon thought, and decided that wishing for that probably wouldn't hurt. He replied "To be a girl for the next day?" finishing the wish and at the same time asking a question. "Yeah. See, you can use yourself to qualify. Now look at your stone." Jon looked at his stone. It had moved from red to orange! So transforming himself into a girl for a day did satisfy the stone, at least for a while. "Now, would you like to go out with me tonight?" asked Pete. Jon, with some idea of how the stone was working, grinned evilly and said "Sure. I wish that Pete and I were going out with each other tonight." Immediately, Pete grew the standard breasts, skirt, and other parts of a girl. Jon looked down at the stone in his hands and it was yellow with just a tinge of orange. "Hey, you tricked me!" exclaimed Pete. "Ahem," grunted Jon. "I cooperated with the stone. It likes to change people into girls. I guessed that if I like girls and the stone likes girl transformations, it would probably do my wish by turning you into a girl." Pete's suddenly higher pitched voice sounded rather sexy. "It could have made you feminine in mind instead, babe... that's a kind of girl transformation." "Well, it didn't. Once I go out with you I should be able to wish you back, but if I don't wait a day the stone will get redder again. I don't want that. Now, in the meantime, what did you want to do on our lesbian date?"