How we cite our quotes: (line number)
Quote #4
But the landlady is a fat, ugly, mean, stupid, unwashed, misanthropic, cheap, drunken bag of garbage. And you may have noticed that I very seldom use profanity, so I can't describe her as well as I might. (140)
Jerry hates his landlady. Is that because the landlady is disgusting? Or is it because he doesn't want to be like her, or to be associated with her? Jerry tweaks Peter about being upper-class, but he seems to dislike the poor people that he lives with. This is what drama critics like to call inner conflict. It's all the rage these days.
Quote #5
PETER: It's so…unthinkable. I find it hard to believe that people such as that really are. JERRY: (Lightly mocking) It's for reading about, isn't it? (145-146)
"People such as that" seems to mean "poor people." And Jerry would be one of them too, probably—the sort of person Peter probably doesn't have to interact with very frequently.
Quote #6
It was as if he had never eaten anything in his life before, except like garbage. Which might very well have been the truth. I don't think the landlady ever eats anything but garbage. (158)
Jerry compares the landlady to her dog and suggests that both frolic in filth. But if the landlady frolics in filth and Jerry lives in her house, then we can deduce that he is frolicking in filth, too. No wonder he's cranky.