Not all my Dad’s jokes were about his Uncle Lubert. One of his favorites: A man in a small town strange to him is looking in vain for the Post Office. He encounters a small boy and asks him “Son, how do you get to the Post Office?” The boy says “I dunno.” The man says “You don’t know much, do you?” The boy says “Yeah, but at least I ain’t lost!”
This useful tale came in handy when someone said “I dunno.” The “You don’t know much, do you” and sometimes “Yeah, but at least I ain’t lost!” followed naturally.