O/T; but, from Lady Stein's "Mandarin" story, and Chinese taught by people with no knowledge of it -- a World War II prisoner-of-war tale. Happened in an officers' POW camp in Germany. One of the miseries of that situation, for many, was prolonged acute boredom: per the Geneva Convention, it was not allowed to put officer POWs to work. Prisoners turned eagerly to learning and teaching all manner of subjects, to give themselves something to do.
A British prisoner -- to alleviate boredom and maybe have a bit of fun -- came up with a prank: he'd offer to teach Chinese, though in fact he knew not a word of the language. He got one "customer", a Polish fellow-prisoner. Basically, the British guy made up words which he thought were sort-of Chinese-sounding; and based the grammar on his memories of Latin from his schooldays, plus some made-up refinements of his own.
All went well at first; but the Pole rapidly turned out to have a formidable talent for languages, and to be a very quick learner. The Brit found himself increasingly run ragged in inventing, and remembering, more and more nonsense "Chinese", to keep just ahead of his frighteningly talented and eager pupil. In the end, it became altogether too much for the "teacher"; he spent many weeks desperately trying, in the confined space which they were in, to avoid the pupil.