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?