Joseph Smith meets Turkish Humor

I was Skyping with a Muslim friend in Turkey.  He asked me to explain the difference between Christianity and Mormonism.  (Thank you, Mitt Romney.)  I gave him a summary.  He said, referring to Joseph Smith, "Anyone can claim to be a prophet."  (To which I readily agreed.)  Then he told me a delightful story to illustrate.

A man in an insane asylum thought he was a messenger from God.  The doctors pondered how they could show him he wasn't.  Finally they approached the man's roommate and said, "Your roommate thinks he is a prophet.  Do you know of any ways we can prove to him that he's not?"  The prophet's roommate didn't hesitate.  "Well of course!  I didn't send him!"