This teenager shares a room with his kid brother.
He's got the upper bunk and the kid has the lower bunk.
One night the teenager sneaks a girl into the bedroom and begins fucking her in the top bunk.
She starts getting loud, so worried, he whispers: "Look, don't be going harder, deeper, my brother might hear and tell on us. If you want it harder say tomatoes, and if you want it deeper say lettuce."
So they're going at it hot and heavy and she's screaming "LETTUCE!" "TOMATOES!" "LETTUCE."
Next morning, the kid says to his brother "Hey, next time you make sandwiches in the bedroom, be more careful last night you dripped mayonnaise all over me!"