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!

Knock-knock
Who's there?
Delores
Delores who?
Delores my shepherd.

Got one better than that?