From the "Seinfeld" episode 120, "The Rye":

FRANK: Let me understand, you got the hen, the chicken and the rooster. The

rooster goes with the chicken. So, who's having sex with the hen?

GEORGE: Why don't we talk about it another time.

FRANK: But you see my point here? You only hear of a hen, a rooster and a

chicken. Something's missing!

MRS. ROSS: Something's missing all right.

MR. ROSS: They're all chickens. The rooster has sex with all of them.

FRANK: That's perverse.