The receptionist tells the psychiatrist that there's a man in the waiting room who claims to be invisible.
The Psychiatrist says, "Tell him I can't see him right now."
Two psychiatrists bumped into each other in the hall. One of them said "Hi." As he walked away, the other muttered, "Hmmm. I wonder what he meant by that?"
A famous ornithologist was asked to be the keynote speaker at the opening of a new bird sanctuary. Since he had a scheduling conflict, however, all he could do was send his egrets.