Tongue twisters are a barbaric but hilarious form of entertainment designed around the simple fact that languages are hard.

Languages are rarely well-designed. Those that are, like Esperanto, sound so awful and are so complex only a small core group of zealots ever want to use them. No matter how tightly the language-lawyers try to keep control over language specifications¹, the end-users keep subverting things. They invent new words and generally pervert the language by altering the meaning of words² or adopting words from other languages³. Computer terms are among the most common English words which are now being adopted into all languages.

These peculiarities at least leave room for some simple fun. Many languages have a mixture of sounds, some that are easy to pronounce, some that are complex, and some that are only difficult when combined with others. Other languages are just flat-out jawbreakers and have no easy sounds at all⁴.

The fun of tongue twisters is inventing strings and combinations of sounds that are hard to say in series. The tongue twister should be repeated multiple times - anywhere from three to ten times is common - as quickly as possible, usually all in one breath. For added effect and bonus points, the good ones are designed in such a way as to trip the tongue into saying bits of absurdity, or even outright crudity, instead of the intended phrase. Such as:

• Fat frogs flying past fast.
• Red lorry, yellow lorry.
• Chop shops stock chops.
• Tim, the thin twin tinsmith.

• The sixth sick sheikh's sixth sheep's sick.

• I'm not a pheasant plucker,
  I'm a pheasant plucker's son,
  and I'm only plucking pheasants
  til the pheasant plucker comes.