Little Johnny’s in class one day, and the teacher calls on students to name things that are not good to put in their mouths. Little Johnny raises his hand, and the teacher calls on him. "A lit light bulb," he says. The teacher says, "Well, you’re right, but do you know why it’s not good for you?" Little Johnny says, "No, I don’t know why, but my mom always tell my dad, ’Turn the light off before you put it in my mouth!’"