JSTOR Daily shares the sordid tale of George Psalmanazar, a white man from France who claimed to be a Christian convert from Formosa, (Taiwan) in the 1700s. How did he pull it off? During this era, Europeans were still exploring various parts of the world, and only a select few had any first-hand knowledge of Asia, Africa, or the Americas. A slightly larger, but still small group may have read about certain expeditions but could hardly be considered experts. Few people knew anything about Taiwan, meaning Psalmanazar could say whatever he wished.
Is there a trickster in your story? A con man or a murderer who blends in by standing out? Take a lesson from George Psalmanazar: create a in-story fictional background that your other characters wouldn’t question.