Many websites such as ChildBeckons.com, LaJollaMom.com and SquiglysPlayhouse.com offer lists of kid friendly knock-knock jokes. Many kids also enjoy creating their own knock-knock jokes, even if the jokes do not make much sense to adults. Knowing the format of a knock-knock joke makes it easier for kids to memorize the jokes, play along with a joke told by an adult and come up with their own jokes.
Good knock-knock jokes follow a structured format. The joker initiates the joke with, "Knock, knock!" The other person responds with, "Who's there?" The joker then sets up the punch line by feeding the respondent an answer. The person responds with the joker's answer followed by, "Who?" The joker then makes a pun out of the response, such as in the water knock-knock joke, or acts like the respondent said something out of the blue and pokes fun at her, such as in the yodeling knock-knock joke.