Me: (upon being told that all was essentially well and curable) Oh, Dr. _______, thank you! I spent five minutes on WebMD this morning, and had myself convinced that I had a hole in my eardrum and was going deaf. Then I decided I should probably find out from a real doctor. Thank you so much!
Doc: (beaming) Well, um, that's the downside of WebMD.
(Note: a slightly modified version of this dialogue also works with librarians)