I agree with you that Rick and Morty isn't a nihilist show, and neither are any of the characters nihilists. Rick is deeply cynical and maybe a philosophical pe

I agree with you that Rick and Morty isn't a nihilist show, and neither are any of the characters nihilists. Rick is deeply cynical and maybe a philosophical pessimist, and he's definitely a moral relativist, but I wouldn't call him nihilist, no. Your first paragraph is a really good set of examples, so I can see now how the characters can be perceived as nihilists. But my personal conception of how nihilism would operate in real life is that it would be intrinsically erratic and dysfunctional, with the nihilist continually struggling against an inherent lack of motivation and a biological drive for self-preservation. In that sense I consider nihilism to the functional equivalent of absurdism and pessimism. Absurdism has essentially the same core tenets as nihilism, but its literature reacts to a lack of intrinsic meaning with flippancy and a declaration that people should ignore that and continually strive for meaning anyway (which is inherent dissonant, but basically don't think about it and live on). From there, nihilism appears to be, in my opinion, what happens when someone encounters the dissonance of 1) no intrinsic motivation anymore, brought about by intellectually grappling with existential despair, and 2) instead of leaving that state, whether through traditional existentialism/religion (Kierkegaard) or through tucking it away and forgetting about it, lives on with it and doesn't commit suicide out of biological necessity. In contrast I think the examples you posed about Seinfeld's characters are more like deep self-absorption or narcissism, and maybe outright sociopathy. In a certain sense it seems like a much more implicit form of the unsettling indifference portrayed in a Brett Easton Ellis novel.