So one of the wayward sons returns home from military service and was telling his kin of all his heroic deeds in the war and about all the marvelous weapons he had used
Then he pulled a hand grenade out of his knapsack and explains how powerful this small baseball sized armament really was. Upon there disbelief he says here I'll show you and pulls the pin and errantly lobs it right through the crescent moon on the shitter door and then B O O M !
Shitter blows clear the hell up in the air and now there's boards and shit raining down all over the yard! And all of a sudden Grandps lands right in the middle of all that shit and stands up and looks at everybody and says
"God Damn I'm glad I didn't let that one in the house!"