I've never seen a movie on Calligula.... why would someone waste the time to make a movie on a madman, let alone multiple additions as you state. Actually, were I got most of what I know about Calligula and the other Roman emperors was from a book about Roman Emperors and how the majority of them led the empire down a steady path of destruction. It also mentions, that only 5 of them were "good" from a historical perspective. I can't remeber the name of the book, or all 5 of the "good" emperors, but I believe they were, Ceaser, Augustus, Tiberius, Constatine... and I can't recall the other one, but I believe he was from Spain, although that might be Tiberius, I don't have the time to try to find out as I'm about to leave for Niagara Falls to go visit family.