Knock-knock jokes are funny. They are popular in almost all English-speaking countries. You always require that fraction of a second to think and find out what exactly the pun is. That's why they are so good to read. No one apparently knows the origin of Knock-knock jokes. The jokes may well date back to the William Shakespeare era. In most cases, the jokes involve a pun or play on words. Read fifteen funny knock-knock jokes that will make you laugh out loud.