I always say that you can laugh with patients but you should never laugh at them. Recently I broke this rule and pulled a patient's leg gently, but I came off worse in the subsequent exchange. Which serves me right!
It was a woman I don't know well as she usually sees one of my partners, but I did know that my partner finds her a bit gloomy and hypochondriacal. She opened the batting by asking me if I was well. I replied "yes", to which she retorted "you don't need to see a doctor, then!" Knowing her reputation I couldn't resist saying "no, which is just as well since I don't know any good ones". Quick as a flash she nodded her agreement, saying "there aren't many".