But he also didn’t like to eat leftovers, or cheese that had to be sliced, or any of the yogurt flavors in the fridge.
-- Narrator (Chapter 1)

Importance: One of the opening sentences of the novel describes Bat’s likes and dislikes. In this scene, he is unhappy because his sister has eaten the last vanilla yogurt, his favorite, and left the flavors that he does not like.

So, between the initials and the earmuffs and the hand flapping, the nickname had stuck.
-- Narrator (Chapter 1)

Importance: Bat received his nickname because his initials spell out the word “bat” and he has sensitive hearing, like a bat. He often flaps his arms when he is excited, somewhat like a bat flaps its wings. Because Bat likes animals, he does not mind having an animal’s name as a nickname.

Mom said they’d have to hand the kit over to the rescue center in a month. But...
-- Narrator (Chapter 6)