Disclaimer: I don't know any Dutch or Afrikaans, and can't vouch for this story, which was told to me some years back by a reader of Linguist List
Once a young man from the Netherlands moved with his family to South Africa, where he was naturally put in the Afrikaans-speaking class. Afrikaans is an offshoot of Dutch, retaining older spellings and word meanings, and with a fair amount of English mixed in (among other languages). He was asked to write an essay describing himself and his family, and then to read out loud to the class. It contained the harmless Dutch sentence "Mij pa fok dieren" (My father breeds animals), which in Afrikaans (under English influence) has a very different meaning!