They've done too many. The worst probably when DS was a toddler and we were at the mall. We passed by a toy store with a truck on display. He pointed at it and said as loud as he can F**K
He had a problem with some of his letters. I had quite a few stares and just wanted to disappear.
ETA: Gladly, he slowly fixed his pronunciation. In Kindergarden, he spelled the same word: Chruck