Derrick

“Feynman did have an extraordinary affinity for his friends’ children. He would entertain them with gibberish, or with juggling tricks, or with what sounded to Dyson like a one-man percussion band. He could enthrall them merely by borrowing someone’s eyeglasses and slowly putting them on, taking them off, and putting them on. Or he would engage them in conversation. He once asked Henry Bethe, “Did you know there are twice as many numbers as numbers?” “No, there are not!” Henry said. Feynman said he could prove it. “Name a number.” “One million.” Feynman said, “Two million.” “Twenty-seven!” Feynman said, “Fifty-four,” and kept on countering with the number that was twice Henry’s, until suddenly Henry saw the point. It was his first real encounter with infinity.”
― James Gleick, Genius: The Life and Science of Richard Feynman