What are examples of puns from Dr. Seuss books?

"Today you are You, that is truer than true. There is no one alive who is Youer than You!" from "Happy Birthday to You!" is a pun on "You are unique." Another one is "Unless someone like you cares a whole awful lot, nothing is going to get better. It's not." from "The Lorax" is a play on "It's up to you to make a difference."