Finding one of her students making faces at others on the playground, Ms. Smith stopped to gently reprove the child.

Smiling sweetly, she said, “Bobby, when I was a child, I was told if that I made ugly faces, it would freeze and I would stay like that.”

Bobby looked up and replied, “Well, Ms. Smith, you can’t say you weren’t warned.”

Source:  http://www.cleanfunjokes.com/pulling-faces-clean-joke-27.html