[wally_bert]

This episode came to mind but the impersonating doctor was trying to do good.

https://www.youtube.com/watch?v=CFfOc0_6KXI

One of my favorite episodes of Streets Of SF.

[robowombat]

Indeed. There were a fair number of such doctors who printed their own diplomas back in the dark ages before any electronic record keeping existed. If a personable and seemingly knowledgeable person showed up in some small city or town in the south or west and hung out his shingle no one asked many questions if he seemed to know what he was doing.