A police officer pulls over a car full of nuns and asks "Why were you driving so slowly?" The nun driver replies "The speed limit is 20 miles an hour, officer." "No, Sister, the speed limit is 70." "Then what are all the signs that say 20 on them?" "This is highway 20. They just mark what highway you are on." "Oh... That explains why the other sisters were screaming back when we were on Highway 166."
I've often started off with a lawyer joke, a complete caricature of a lawyer who's been nasty, greedy, and unethical. But I've stopped that practice. I gradually realized that the lawyers in the audience didn't think the jokes were funny and the non-lawyers didn't know they were jokes.