There is a story about how Einstein was traveling to universities in a chauffeur driven car and delivering lectures on his theory of relativity. One day while in transit the chauffeur remarked : "Dr.Einstein, I've heard you deliver that lecture about 30 times. I know it by heart and bet i could give it myself".
"Well. I'll give you the chance," said Einstein. "They don't know me at the next school, so when we get there I'll put on your cap, and you introduce yourself as me and give the lecture