“‘You can learn a lot about yourself by taking care of another species,’ she told me on the way home the day she got me. ‘You’ll teach those kids a thing or two.’” 

This quote emphasizes the central theme of the novel. While Ms. Mac was talking about the children taking care of Humphrey, Humphrey takes it to mean him taking care of the children. This frames Humphrey’s interactions with the humans in the novel. 

“But she doesn’t know my secret: The latch on my cage door doesn’t work. It never has. It’s the lock-that-doesn’t-lock.”

The “lock-that-doesn’t-lock” plays an important role throughout the novel. It allows Humphrey a level of autonomy that would otherwise be impossible. If Mrs. Brisbane decides to get rid of him, Humphrey will leave on his own terms. 

“‘Oh that’s right,’ he replied as if we were having a real conversation. ‘Mrs. Brisbane came back today. She is a good teacher, you know, Humphrey. Wish I’d had a good teacher like her.’”

This quote is the first indication that Humphrey gets that Mrs. Brisbane is indeed a good teacher. The perspective the book gives concerning Mrs. Brisbane is influenced by the negative perception she has of Humphrey. In addition, this gives some insight into Aldo’s educational past.