An invisible man is here to see you
Nurse: Doctor, there is an invisible man in your waiting room.

Doctor: Tell him I can't see him now. Next.

A little change
The patient shook his doctor's hand in gratitude and said:"Since we are the best of friends, I would not want to insult you by offering payment. But I would like for you to know that I had mentioned you in my will.""That is very kind of you," said the doctor emotionally, and then added, "Can I see that prescription I just gave you? I'd like to make a little change..."