Knock, knock jokes can be some of the dumbest and yes Rick tells one. Gary talks about how his kids learned the art of the knock, knock joke too. What's the point? It reminds us of a  promise from God's Word. 

"Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you: For every one that asketh receiveth; and he that seeketh findeth, and to him that knocketh it shall be opened" Matthew 7:7-8.