Nuclear bombs are nothing but potential. Now I'm what comes after. Now I'm the three-headed frog. The radioactive fallout.”
-- Simon (chapter 2)

Importance: Simon is comparing himself to the nuclear bomb and to the result of a nuclear detonation. He felt he had a huge amount of potential before the epic battle that took place in the previous novel of the series, but now is an embodiment of the terrible result of a nuclear blast.

And I know this makes me a shit, but my first thought is that Simon and I have been given a reprieve. Like the Grim Relationship Reaper came and accidentally took Penelope and Micah instead of us.”
-- Baz (chapter 14)

Importance: Penny has just announced that she and Micah broke up, and this is Baz's reaction. The author tends to make humorous observations about many aspects of life for these characters, including this reference to the “Grim Relationship Reaper.” Baz's reaction demonstrates that...