I explained to my French class of 7th graders that they were mispronouncing grandfather. Instead of "grand-père" they were saying "grand Pierre." I said "If you say 'grand Pierre' instead of 'grand-père' then you aren't talking about your grandfather, you are talking about your big peter."
During an after school tutorial session, I had several students making up a French test. I wanted to know if all the test takers had finished so I could go to the board and write some verbs and vocabulary and review with the other kids. It was silent in the room as some took tests and others made flashcards or wrote make-up work. I looked up and asked, "Are my testees gone?" (Only one 6th grade girl heard me and she just looked up and in a blasé way said, "Oh, yeah, Madame, that's a good one.")