In kindergarten, they moved our "big toy" playground, so one day in carpool we pulled up & it was gone, so I said:
"Holy sh**, the big toy's gone!" I didn't know what the word meant, and I said it brightly and in an upbeat tone. I still remember saying it because I remember the look on the carpool driver's face that day as he turned around in his set! I don't remember him saying anything, but I immediately thought "Oh, wait--is that word bad?"