Also known as the coolest and most insensitive way to break up ever conceived by man. A sex move that's notoriously hard to pull off. You'll need a window in your bedroom, on the ground floor, a cupboard for a friend to hide in, and a girl.
Start doing the girl doggy-style, facing the window, and then have your friend quietly sneak out of the cupboard and trade places with you without her noticing. Then exit the room, walk in front of the window, and wave to her. Bonus points if you're still naked when you do this.
"Dude, I finally managed to pull off a time paradox! She'll probably never speak to me again, but it was worth it!"