Think again before making faces.

Finding one of her students making faces at others on the playground, Miss Smith stopped to gently reprove the child. Smiling sweetly, she said, "Bobby, when I was a child I was
told if that if I made ugly faces, my face would freeze and stay like that".

Bobby looked up and replied, "Well, Miss Smith, you can't say you weren't warned."

Source: http://www.amusingfacts.com/humour