I looked at [Fudge] and thought about having to go through it all over again. The kicking and the screaming and the messes and more – much more. I felt so angry that I kicked the wall.”
-- Peter (Narration) (Chapter 1 paragraph 5)

Importance: This quote sums up Peter's feelings about both his troublesome younger brother and his concerns about bringing another younger sibling into the family. It is also a manifestation of the book's thematic interest in dealing with big feelings - in this case, anger, fear, and resentment.

I know it’s stupid, but for just a minute I wished I could be Mom’s baby again, too.
-- Peter (Narration)  (Chapter 2)

Importance: This quote is taken from a sequence describing the family dynamic just after the birth of Peter's baby sister Tootsie. Just prior to this moment, Fudge has been actively pretending to be a baby, much to Peter's annoyance here, though, Peter sees the attention both Tootsie and Fudge...