I loved that it was a detective show that was about being obsessed about the minutia of memory and paperwork, about mercurial changes in personalities and roles during the years you were growing up, and about 2nd gen immigrants and race. Hell they had an episode about "the model immigrant".

Does Ginsberg count as a minor character? Always had a soft spot for him, and his exit and possibly horrible off-screen life that he will lead in the 70's was the 2nd saddest thing in S07 of the show.
And yes Carla. The quiet moral authority watching in dismay as Betty's self destructiveness ruins the lives of her…

My bad Cheever and Yates were mentioned.

Les Baxter??
Literally every other episode has music cues dedicated to him.
Richard Yates and John Cheever need a call-out to.