An accountant is having a hard time sleeping...
An accountant is having a hard time sleeping and goes to see his doctor."Doctor, I just can't get to sleep at night." "Have you tried counting sheep?""That's the problem - I make a mistake and then spend three hours trying to find it."

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.