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.
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'.