The rain in Spain stays mainly in the plain...

Have you ever seen the movie My Fair Lady? It's an adaptation from the play Pygmalion by George Bernard Shaw (1913) about a Cockney flower seller, Eliza Doolittle, who was trained by a phonetician, Higgins, to enable her to pass as a lady. The experiment is successful, but not without some repercussions. In the story Eliza has to repeat some tongue twisters to correct her accent.

According to Webster's Dictionary, Tongue twister is a word, phrase, or sentence difficult to articulate because of a succession of similar consonantal sounds

An example of English tongue twister:

How many cookies could a good cook cook If a good cook could cook cookies?
A good cook could cook as much cookies as a good cook who could cook cookies.

...and Indonesian tongue twister:

Ular melingkar-lingkar di pagar
(The snake coils around the fence)

Michael Reck's site compiled thousands of tong twisters from all over the world, from Acholi to Zulu!

For those of you who are learning new language(s), I encourage you to visit his site as this is a way to train your speech ability and to see if your pronounciation is up to scratch.

and now, let's repeat after Eliza:

In Hertford, Hereford and Hampshire hurricanes hardly ever happen.