"Horny Madness" joke

A guy is nearing the end of his senior year in high school.
Unfortunately, he still has to share a room with his younger brother who is only 9 years old.
One night he decides to bring his girlfriend home for a little fun. They have bunk beds and the guy notices that his little brother is already asleep on the lower bunk, so he and his girlfriend climb up to the top bunk.
As you might expect things start to heat up. The big guy remembers that his little brother is sleeping below, so he tells his girlfriend to whisper:
"
lettuce"
if she wants it harder and "
tomato"
if she wants a new position.
"
Lettuce!!! Tomato!!! Lettuce!!! Tomato!!!
Lettuce!!! Tomato!!! She screams.
Lettuce!!! Tomato!!! Whoa.
PULL IT OUT!!! PULL IT OUT NOW!!!
I can't get pregnant.
Then the little brother shouts up.
"
Hey, would you guys stop making sandwiches up there!
You're getting mayonnaise all over my face!"