Stephen Scott’s Why Do They Dress That Way? is an extensive and very interesting look at dress customs among plain religious groups.  In the book, Scott relates an amusing anecdote:

“…away from their home environment, plain people are often mistaken for nuns or priests and vice versa.  One group of plain girls from Pennsylvania took the train to visit friends in Iowa.  Since there was a long layover in Chicago, they decided to take a taxi to see some of the sights.  The taxi driver, thinking they might be nuns, asked, “Are you sisters?”  One of the girls misunderstood the nature of the question, [and] replied, “No, but some of us are cousins.”