When a man ejaculates into the belly button of his partner forming a reservoir of semen, the man then pisses out a kidney stone through his penis into the reservoir, thereby creating the noise of a coin being dropped into a wishing well.
Boy: Hey baby where do you want me to finish?
Girl: In the belly button...
Boy: ok but i think i have to piss a kidney stone, lets make a Puerto Rican wishing well.
Girl: ok and maybe tomorrow we can try a mongolian horse race.