Factual error: Adam is outside playing tennis at school. The episode takes place "February 1980 something" and the students are all in shorts and the trees and grass are all lush and green. This wouldn't be the case in February in the suburbs of Philadelphia.
Factual error: Adam narrates that it is "April 5th, 1980-something" and is going to see the new Michael Keaton "Batman" movie with his Grandpa, but "Batman" was released on June 23rd, 1989, not in April of that year.
Uncle Marvin is teaching Barry and the JTP hand signals to use on Wall Street. It is obvious he is making up the gestures, but when he says "Tell her that I'm sorry" he is using an American Sign Language sign for 'bullshit'.