After WWII, Albert Einstein moved to the US and would travel from university to university to deliver talks on his theory of relativity. For these trips, he had a Chauffeur named Bob who'd drive him from school to school. Bob would also sit in and listen to the lectures. One day, on their way to a lecture, Bob turns to Einstein and says - "you know, I've heard your lecture so many times, I could probably give it at this point." To which Einstein replies - "maybe you should - let's switch!". Given it was the 1950s and pictures of einstein weren't widly distributed, they figured why not. So about a mile from the college, they switch spots, and Bob gets up to give the lecture, while Einstein, dressed as the Chauffer, takes a seat in the back of the auditorium.
Much to Einstein's surprise, Bob is spot on. He delivers the talk perfectly, and even answers the first few questions from the audience. Of course, most of the questions are the same one people usually ask, and so Bob already knows the answers. But then, the department chair asks a more difficult question, one that Einstein knows Bob can't possibly answer. He waits with baited breath to see what Bob would do. Bob looks at the professor and without missing a beat, says:
"That's such an east question, even my Chauffeur can answer it!"