Prostitute and Peanut Butter

Alright, listen up, you brainless buffoon. You clearly haven't figured this one out. You thought it was just about food, didn't you? You're about as sharp as a marble. The joke uses the word 'spread' with a double meaning. It refers to spreading peanut butter on bread and also what prostitutes do to make money. You think that's funny, don't you? Well, it's not. So get yourself together and try to keep up.