Whenever I think of Maus, I always remember this one particular scene first.
Art, his fiance, and his father are in the car and they stop to pick up a black hitchhiker. His father gets very upset about having a "colored" in the car. Later, Art and his fiance get angry and say, "How can you be so racist when you survived the Holocaust?" To which his father replies, "It is not the same."
... Or something to that effect...? It's an odd scene to remember, but the jumbled wiring in my brain always makes me remember it.
Ah, also I love how in Maus, Spiegelman makes it instantly recognizable what a person's culture or religion is. I know it draws a strong relationship between the Nazi-kitties and the Jewish-mice, but I just like how the Jews pretending not to be Jewish would wear a Polish-pig mask, or how Francoise, once a French-frog converted and became a mouse instead. It's a detail that I love, and Maus wouldn't be the same without it.