What to read after Hippopotamister?

The zoo isn't what it used to be. It's run down, and Hippo hardly ever gets any visitors. So he decides to set off for the outside with his friend Red Panda. To make it in the human world, Hippo will have to become a Hippopotamister: he'll have to act like a human, get a job, and wear a hat as a disguise. He's a good employee, whether he's a construction worker, a hair stylist, or a sous chef. But what he really needs is a job where he can be himself.