It's the year 2389, and martian and earth couples are living peacably side by side. One day, an earth couple and a martian couple are having lunch and the subject of sex comes up. Because the earth couple has so many questions, the couples decide to swap partners for a week. A little later, the martian man and the earthwoman are alone in a bedroom, getting undressed. When the martian is naked, the woman is surprised that his penis is only 1/2 inch long and a 1/2 inch wide.
"Hold on," says the martian, who slaps his face, which makes his penis grow longer with each snap. "Oops, it's not wide enough yet." He pulls his ears, and with each tug, his penis grows wider. "All set!" he says, and the martian and the woman have incredible, mind-blowing sex. Later, the woman meets up with her husband, and asks him how it was.
"Well, it was fine. But I have a headache now because she kept pulling my ears and slapping my face."