The teller will have a group of friends who know what is going to happen. The teller then asks somone who is not in on the joke if he would like to hear a joke. The teller tells a story that makes absolutely no sense and is not humorous, and finishes it with the line "No soap, Radio!". The friends in on the joke then burst out into laughter.
The friends in on the joke then get to see the reaction of the friend not in on the joke. Will he laugh at a pointless joke to try to fit in, or will he make an ass out of himself trying to understand it?
People in on it: Ha ha ha!
Not in on it: *unsure* Ha, ha?
All others: Ha, moron.