There can be only ONE

You cross the room to this other you. Both of you stare back and forth at each other. "Are you me?" you ask. "I mean, are you still Jane deep down, or are you, completely, totally me?"

"I can't quite tell, John" the other you say. "I remember being my girlfriend—your girlfriend—oh, it's so hard to tell—but those memories feel like they happened to somebody else. I feel like I've always been who I am now, and being her is a dream."

"That's amazing," you say. "I was only joking around, I never meant for it to go quite like this." You reach up to touch the other's face.

As soon as you touch his cheek, it feels like a bolt of lightning passes from his body into yours. You feel dizzy at first, but then it starts to feel like the room is growing. No, not growing: you're getting shorter. And your shirt becomes tight as breasts sprout from your chest. Your whole body transforms. Your scalp feels warm as your short, dark hair grows into long blonde locks. Your backside turns wide, your hips get further apart, and when you look in the mirror, your face has turned soft and feminine.

You've turned into your girlfriend.

You and your girlfriend—sorry, you and your BOYFRIEND stare at yourselves in the mirror. You swapped straight across. This has gone further than you ever imagined.

You reach up and touch his face again. Nothing happens. Whatever transformed you, it was a one-shot deal. You two look at each other for several long minutes.

"How did that happen?" you ask. "Neither of us asked for that change."

"Maybe when you turned me into someone who already existed, there could be only one of that person, and the other of that person had to be me," he says. "The old female me, I mean."

"So what do you figure?" you ask. "Should we change back?"