What is a ���knock knock joke���?
It���s a joke with a specific format that requires interaction between two people. The person saying the joke begins with the phrase ���knock knock��� and the other person responds with ���who���s there?��� The person asking the joke then gives the setup, and the other person repeats back the setup verbatim and adds the word ���who��� at the end. The person asking the joke then delivers the punchline. An example of a knock knock joke is: 
 Knock knock
 Who���s there?
 Orange
 Orange who?
 Orange you glad I���m only doing one knock knock joke!?