Barney, the cute purple dinosaur, is Satan.

Proof:

Given: Barney is a cute purple dinosaur.

Extract the Roman numerals: (and remember that the Romans 
had no letter 'U', they used 'V' instead)

CVTE PVRPLE DINOSAVR
CV    V  L  DI    V

Add them:
100 + 5 + 5 + 50 + 500 + 1 + 5 = 666

Q. E. D.  We suspected it all along.