Joke: Lettuce And Tomato-Fool joke

This guy has to baby-sit his litle brother, and when his parents leave they say, 'Now, don't you bring your girlfriend over, or you're in big trouble, young man.'

The guy promises he won't, but as soon as his parents left he puts his little brother to bed and calles up his girlfriend. She comes over and they get down in the bed to fuck each other, and she says, 'Okay, lettuce means harder and tomato means faster.' So they go at it, shouting, 'Lettuce, tomato! Lettuce, tomato!'

The little brother chooses this moment to come into the bedroom saying he can't sleep, and asks, 'What are you doing?'

The guy, thinking quickly, says, 'Oh, we're making a sandwich.' So they continue to bang the bone-dance, shouting, 'Lettuce, tomato! Lettuce, tomato!'

The little brother put his hand to his cheek and said, 'Yuck, you got mayonaise on my face!'