So, a kid happens to see his mom naked and asks,...

So, a kid happens to see his mom naked and asks, pointing to her vagina, "What is that?" The mom replies, "That is my house." She responds. A little while later the kid sees his dad naked and asks the same question. "Well, son, that is the Big Bad Wolf," responds the dad. Some time goes bye and the kid goes into his parents bedroom, while they are amidst sex. "Hey mom," pipes the kid, "watch out! I think the Big Bad Wolf just walked into your house and shot the piggie!"