Character mistake: When Ray and Winston are driving across the Brooklyn Bridge around midnight in the Ectomobile, Ray quotes a verse of scripture claiming to be "Revelation 7:12". What he quotes is actually Revelation 6:12. (01:03:38)
Character mistake: Peter tells Egon over the phone that he gave Dana "300 cc of Thorazine." Besides the funny implications the movie ignores on how and why he was in possession of it, Venkman says "cc", but the drug is dosed in mg, so at the very least Venkman misspoke (that'd be 1/3 liters!). The line is not in the shooting script and other sources like the novelization just say that Dana had some valium lying around. (01:02:30)
Character mistake: Meeting Dana at the Lincoln Center fountain, Venkman tells her that Gozer was a deity worshipped in 6,000 BC by Hittites, Mesopotamians and Sumerians. There are no historical accounts of those specific populations dating back to that ancient of a date, or writing of any form for that matter. (00:43:40)
Suggested correction: Venkman said Mesopotamians, not Babylonians. The Mesopotamian civilization existed in 6500 BC so his information would be accurate in that aspect.
You are absolutely right, I have misquoted the movie there and I just fixed it thanks to your correction. "Mesopotamians" is just a generic denomination, though, so saying that Gozer would be worshipped by the Hittites in 6000 BC, and then list a generic name for the inhabitants of the area and then the Sumerians (generally accepted as the first organized civilization of the area, still much after the proposed date) doesn't seem to be quite accurate.
A valid point of view from both of you, however, it's established that Dr. Venkman is the least knowledgeable in paranormal history so it's possible he listed the groups out of order. As is rightly pointed out, Mesopotamia was a generic listing, like saying Americans, so maybe if he said Mesopotamians first, then the other groups, the quote would make sense?
I completely agree that he's the least knowledgeable of the bunch by far and it is well-established and reinforced in the same scene since he needs Dana's help to read "Hittites." Read, because he's not quoting from memory; he's reading (presumably something Egon or Ray had to write down for him). As you say, "if" he said Mesopotamians first, maybe it would have made sense (but it's not what he says), and even then, using your example, saying "in 1000 BC, Manitou was worshipped by the Sioux, the Americans and the Apache" just sounds wrong. (I know that by 'Americans' we mean generally the US population and feel free to add 'native' to it, then again Hittites established their civilization when the Sumerians were wiped out already, and that's 4 millennia past the date - it is what happens making a word salad in a small sentence that has to register just superficially for the audience).