1. Start with the given:
CUTE PURPLE DINOSAUR
2. Change all U's to V's
(which is proper Latin anyway):
CVTE PVRPLE DINOSAVR
3. Extract all Roman Numerals:
CVVLDIV
4. Convert into Arabic values:
100 5 5 50 500 1 5
5. Add all the numbers:
666
6. Thus, Barney is Satan