This easy form of laughter is popular not only in the U.S., but the United Kingdom, Australia, South Africa and the Philippines. It may sound a little different, for instance in France, they begin with "Toc-Toc", and the Dutch say, "Klop-klop". But knock-knock jokes are unknown in Brazil, India and Germany. Too bad for them, 'cause they wouldn't understand this at all!

Who's there?
Delores who?
Delores my shepherd.

Got one better than that?