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.

1stPerson: "Do you know anything about...
1st Person: "Do you know anything about this fax-machine?"
2nd Person:"A little. Whats wrong?"
1st Person: "Well, I sent a fax, and the recipient called back to say all she received was a cover-sheet and a blank page. I tried it again, and the same thing happened."
2nd Person: "How did you load the sheet?"
1st Person: "Its a pretty sensitive memo, and I didn't want anyone else to read it by accident, so I folded it so only the recipient could open it and read it."