She Is a Thistle Sifter is a really difficult tongue twister. Try to say this one fast...
She is a thistle sifter
and she has a sieve of sifted thistles,
and a sieve of unsifted thistles,
and the sieve of unsifted thistles
she sieves into the sieve of sifted thistles.
Because she is a thistle sifter.