I have a friend who is currently in his 4th 1st year med school. Yes, he is in this fourth University, attempting to pass his 1st year meds. His facebook is full of selfies of himself in scrubs, stethoscope always visible, taken from some of his hospital visits. This guys loves talking medical terms, and no doubt would volunteer and identify himself as a 'doctor'.
People like this are the reason why FAs should always ask for credentials.