Tongue twisters are words or a sequence of words that are difficult to pronounce, especially rapidly, because of alliteration or a slight variation of consonants sounds:

Fred's friend Fran flips fine flapjacks fast.

Sam shaved seven shy sheep.

Any noise annoys an oyster but a noisy noise annoys an oyster more.

If a dog chews shoes, whose shoes does he choose?

Can you speed it up and read it as fast as you can?