This reminds me of a scene from an old Andy Griffith Show episode that, for no good reason, has been relegated to long-term storage in my brain.
Andy and Barney are checking into a hotel somewhere for a cop convention. The receptionist says "Thank you Mr. Taylor. Thank you, Mr. Fife... oh, excuse me, DOCTOR Fife!"
Andy incredulously looks at the sign-in book and notes that Barney has appended an "M.D." to his name - after which Barney sheepishly explains it stands for "Mayberry Deputy".
(okay, in all likelihood I'm the only person here who thinks that's funny...)