Fisrt off, let's start with what we know:

Barney = CUTE PURPLE DINOSAUR

Then, because when dealing with evil you have to use dead languages, we'll change all the U's to look like V's:

Barney = CVTE PVRPLE DINSAVR

Then we extract any letter that could be a Roman Numeral:

Barney = C V V L D I V

Almost there - change the roman numerals to arabic:

Barney = 100 + 5 + 5 + 50 + 500 + 1 + 5

And then we add the numerals to get, yep, you guessed it - 666!

*I'm not sure who the original author is, but it can be found here - http://www.geocities.com/h2lee/barney.html.*