666 refers to BARNEY, the Cute purple Dinosaur, I'll prove it:
The Romans had no letter 'U', and used 'V' instead for printing, meaning the Roman representation would for Barney would be: CVTE PVRPLE DINOSAVR
CVTE PVRPLE DINOSAVR
Extracting the Roman numerals, we have:
CVTE PVRPLE DINOSAVR
CV V L DI V
And their decimal equivalents are:
CVTE PVRPLE DINOSAVR
CV V L DI V
100 5 5 50 500 1 5
Adding those numbers produces: 666.
666 is the number of the Beast.
Proved: BARNEY IS SATAN!