What does the joke of frog and crab mean?

The British Earl's joke about frogs and crabs is a classic China joke. Its meaning involves the use of puns and homophonic words to create humorous effects.

The joke goes like this:

The count asked the Jiujiang guest, "What are you doing here?"

Jiujiang guest replied, "Come and buy frogs."

The count said, "This is not a frog, but a crab."

Jiujiang guest said, "What bad luck! Frogs and crabs have the same pronunciation and ran away in vain! "

The key to this joke is that the pronunciation of "frog" and "crab" in Chinese is very close, so Jiujiang guests mistake crab for frog. When the count told him that it was a crab, Jiujiang guests felt unlucky because he thought he was going to buy a frog, but he bought a crab. It is through this misunderstanding and the pun meaning of language that the joke has a humorous effect.