My very naughty husband has taught me a few swear words of Malinke. When he was on the phone to his family (including his venerable old mum!) he begged me to demonstrate. I was most reluctant but he insisted, so I said, "Eh boh dah! Ee air eh!" (F*** off and the same to you) There were loud shrieks of delight and much laughter from the other end, and I was made to repeat it again and again as different family members came on the phone to enjoy it. I was like a performing circus animal!
When I was teaching,I took no end of pupils 40 at a time (12 yr olds) on week-long visits to France. We stayed in Etretat in Normandy. In the evenings my co-helpers and I would sit in the café and were served by some rather stand-offish people. But I couldn't resist letting loose in fluent French to them and they were amazed. But they expressed their appreciation by bringing me a huge bowl of blooming snails. Yuk!