[NSFW] An alien couple visits the earth and asks a human couple if they want to do wife-swapping.

They agree and the day after the human woman asks her partner how it was. He says that it was really weird and asks her how her night was. She answers: "It was the best sex i ever had. He twisted his right ear and his penis became bigger and bigger and by twisting his left ear, it became smaller and smaller." After hearing that he says: "This explains why she twisted my right ear the whole night"