Try saying “red whistle yellow whistle” ten times in eight seconds,it’ll mess your head up.
Good luck.
Phil.
Thanks Phill but ma heed’s messed up fine already
A good diction exercise! An even harder one (and probably where yours came from?): red leather yellow leather. I can only say it if I pause between words! 
I remember the one as a kid of Sally selling Susatos by the sea shore.
Wait…
…a pretty fairly pleasing flute…
(ten times very fast)
And I thought this was such a nice bunch of people.
How can you inflict such torture on unsuspecting, innocent bystanders and still look at yourselves in the mirror in the morning? Harrumph!
This is a repeat from an earlier thread, but in case you missed it:
Pitter Paper
Pitter Paper peeked or parker peckled paupers
Or packer peckled paupers pitter paper peeked
Aft Pitter Paper peeked or packer peckled paupers
Ware aster packer peckled paupers debt pitter paper peeked?
(Must be read aloud to be appreciated.)
How can you inflict such torture on unsuspecting, innocent bystanders and still look at yourselves in the mirror in the morning? Harrumph!
We wear masks to bed.
I’m not a pheasant plucker,
I’m a pheasant pluckers son,
I’m only plucking pheasants ,
til the pheasant plucker comes. 
uh… nice one Gypsy.
I’m a sheet slitter
I slit sheets
I’m the best sheet slitter
In the whole sheet-slittin’ world
Well.
I’m na the pheasant plucker,
I’m the pheasant pluckers daughter.
an I,m just pluckin pheasants,
like a pleasent plucker aughter. 