During World War II, physicists working on the development of the atomic bomb were naturally well aware of the grim context of their activities and tried to lighten their load with some macabre word games. One was to imagine what the the last words of each of their number might be. One individual in particular gave them a problem - Egon Bretscher. He was notably pessimistic about his health and no one could think how to turn this into his last words. Then, one day, he provided the answer himself. He arrived at the Cambridge lab and observed, 'I don't know what's wrong with me today. I feel so well.'

My source: Rudolf Peierls, Bird of Passage, Princeton University Press, 1985.