Al Franken was about to give a speech to a large crowd. He was accompanied by a sign-language interpreter. He started by acknowledging the interpreter with some remark: "You do great work. Thanks for coming."—or something like that. Then he turned back to the audience and began his speech as follows: (I'm paraphrasing here.)

"You know, this guy Franken is such an idiot, there's no point in translating what he's saying. I know it will just be a big bore. I talked to him backstage, and he really is an airhead. He just goes on and on...."

The audience was silent at first (puzzled, no doubt), and then ripples of laughter began to spread as people figured out that he was playing a joke on the interpreter, who had to repeat everything he said!