There once was this Vietnam vet who still occasionally had very vivid flasbacks.
The man worked as a dentist and one day, he was doing a normal check-up, when a flashback hit him.
He went crazy and repeatedly stabbed the patient. Needless to say, he was fired and needed another job. The vet tried to think of places that wouldn't ask too many questions, so he walked down to the local McDonald's and applied for a position.
They hired him and the first few weeks went well. But one day he was cooking a cheeseburger when another flashback hit him and he stabbed the hamburger into pulp. One of his co-workers turned and asked him with one question: “Are you a dentist?”