Little Johnny

The teacher asks everyone in the class to demonstrate something exciting. When Johnny's turn came, he walked to the blackboard and drew a small dot.

"What's that?", the teacher asked, puzzled.

"It's a period."

"Well, I see that, but what's exciting about a period?"

"Darned if I know, but this morning my sister said she missed one... Dad had a heart attack, mom fainted, and the guy next door shot himself."

(source: wikipedia)