We are all wearing masks. That is what makes us interesting.”
-- Narrator ("Introduction" paragraph 16)

Importance: This quote is Gaiman’s opinion on human interactions and writing. We all pretend something about ourselves.

The heart is greater than the universe, for it can find pity in it for everything in the universe, and the universe itself can feel no pity.
-- The Duke (“The Return of the Thin White Duke” paragraph 32)

Importance: The Duke realizes why his answer was wrong but explains why the heart is the right answer.

Sometimes I think that truth is a place. In my mind, it is like a city: there can be a hundred roads, a thousand paths, that will all take you, eventually, to the same place. It does not matter where you come from. If you walk toward the truth, you will reach it, whatever path you take.”
-- The Dwarf ("The Truth is a Cave in the Black Mountains" paragraph 35)

Importance: The dwarf explains his opinion of truth which leads his companion to explain his.

I remember Icarus. He flew too close...
-- Narrator ("The Man Who Forgot Ray Bradbury” paragraph 12)