Two women were sitting on the front porch of a home and watching the neighborhood children (their sons included) playing a game they called telephone.
The way telephone works, is one person says something and whispers it into the ear of the next child, who in turn whispers what he heard into the next ear. This continues all the way down the line, hoping that the end result would be the same as the beginning phrase, or wildly different.
The women, enjoying a cigarette and watching this, couldn't help but enjoy that their children were playing so well together.
So the first kid makes up a phrase, and passes it on. It continues all the way down the line.
Once the phrase reached the last kid, he reached into his underwear and exploded, killing all the children.
One mom looks at the other and comments "Oh, our kids just blow up so fast."