One day, Albert Einstein had to speak at an important science conference. On the way there, he notices that his driver looks a bit like him.
"I'm sick of all these conferences", Einstein tells him. "I always say the same things over and over!"
The driver agrees: "You're right. As your driver, I attended all of them, and even though I don't know anything about science, I could easily give the presentation in your place."
"That's a great idea!" says Einstein. "Let's switch places then!"
So they switch clothes and as soon as they arrive, the driver dressed as Einstein goes on stage and starts giving the usual speech, while the real Einstein, dressed as the car driver, attends it.
But there is always one smart arse in the crowd who wants to impress everyone and thinks of a very difficult question to ask, hoping that the presenter can't answer it. So this guy stands up and interrupts the conference by posing his very difficult question. The whole room goes silent, holding their breath, waiting for the response. The driver looks at him, dead in the eye, and says :
"Sir, your question is so easy to answer that I'm going to let my driver explain it to you."