Funny Dirty Joke

A Boyfriend texts his Girlfriend saying "Hey babe you wanna come over and have sex?"
Girlfriend texts back "Duh!"
So the girl goes over her Boyfriends house, and right before they get into it, he sets the boundaries. "Ok, so my little brother is home, and I have bunk beds. He's on the bottom bunk. If you want it harder, you say tomato. If you want it faster, you say lettuce, and if you want to moan you say any other ingredients that would be on a sandwich."
So they're up on the top bunk having sex, and she's yelling "Tomato! Tomato! Lettuce! Lettuce! Cheese! Cheese!"
Well the little brother is still on the bottom bunk and yells "Hey can you guys knock it off, your getting Mayonnaise all over me!!!"