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.

After surgery
As the lawyer slowly came out of the anesthesia after surgery, he said, "Why are all the blinds drawn, doctor?"

"There's a big fire across the street," the doctor replied. "We didn't want you to think the operation was a failure."