In "Man on the Moon" Danny DeVito's character is trying to convince Andy to join the series "Taxi" and behind them on his office wall there is a framed photo of Bob Newhart and Mary Frann from the show "Newhart". Andy joined "Taxi" in 1978..."Newhart" didn't come along until 1982.
Who says the Bob and his friend didn't know each other before Newhart? NBC was affiliated with Bob. Or, that is something put in the movie for a reference.