Math
My college roommate was Math Advisor for A Beautiful Mind. It was striking to see Dave's handwriting again on blackboards, notebooks, and dorm windows. But it was more surprising to see how thoroughly Russell Crowe channels Dave's mannerisms in scenes meant to communicate "brilliant mathematical intoxication." (Good model)
We're used to seeing actors do Roosevelt or Churchill or JFK, but it's very unsettling to see a great actor do this guy with whom you used to share a double in Willets and Worth.