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."