Sad thing about Caligula is originally it was filmed as a more serious movie that would embrace the pornographic nature of Suetonius' account (which many scholars question the accuracy of) by adding some nudity (which was also a common tactic used in that era of film to draw in audiences.) Hustler was trying to expand their media operations so they started dabbling in legit film making and not just the pornographic kind. They basically lied to the production team about how raunchy they were going to make it and then edited in addition porno-grade content after the fact. McDowell has spoken about this in interviews over the years. I couldn't finish watching it cause the additional porno clips just drag on too long and aren't really anything novel in the age of internet porn and infinite fetishes.

Fortunately there are some better takes on Caligula these days. Even I, Claudius misses the mark at times (again often borrowing the more scandalous bits from Suetonius that should probably be disregarded as anti-imperial propaganda.) A german professor wrote a book about Caligula thats a far more accurate read on what happened.