Humphrey, the beloved class pet of Longfellow School’s Room 26, has been entertaining young readers since 2004, when he made his debut in Betty G. Birney’s The World According to Humphrey. In the big-hearted hamster’s second outing, Friendship According to Humphrey, Og the Frog arrived to share class-pet duties. Now, after giving Humphrey top billing in 13 books for middle grade readers, seven chapter books, and two nonfiction books, Birney offers Og a turn as narrator in Life According to Og the Frog, which is due out this month. The amphibian daydreams about his former life in the swamp, snacks on crickets the friendly students drop in his tank, and composes chirpy poems and songs, but when the class debates whether Og should be returned to the wild rather than live in an indoor tank, he frets he may have to bid farewell to his school life. Birney spoke with PW about the genesis of her original series and its new offshoot, and the messages her latest novel imparts.

What initially sparked the idea of writing in the voice of a classroom pet?

When kids ask me why I began writing about Humphrey, they are often disappointed that it was not because I have a hamster named Humphrey! I’ve never owned a hamster, but the inspiration for the character first came to me years ago, when my son had a science teacher whose classroom was lined with cages and tanks filled with all kinds of animals. In fact, the teacher sometimes wore a boa constrictor around her waist! I remember looking at those animals and wondering what they think about, and what they hear and see. I decided it would be fun to write a book that would look at a classroom through the eyes of the class pet, and began making lots of notes as ideas came to me—and it grew and grew until it finally became a book.

Why did you select a hamster as that class pet?

I did think about other options, but I knew that hamsters are among the most popular class pets—they are relatively easy to take care of and aren’t prone to illnesses. And I wanted my character to be agile and able to do things, and hamsters do fun things like spin their wheels. They’re great acrobats and escape artists—so I knew that Humphrey would be able to get in and out of his cage. A turtle would have been much too slow, and difficult to write in terms of getting it out into the world. And hamsters are small, furry and cute—I’ve heard many fans say that’s what they love about Humphrey.

So on to Og: why did you opt to add a second pet to Room 26?

Well, I had written The World According to Humphrey as a one-off—I didn’t pitch it as a series—and my editor, Susan Kochan, asked for a second book before the first came out. I began thinking, “What if there was a second pet brought into the classroom, one that was very different from Humphrey?” The fact that they have very distinct personalities is the key to their relationship. While Humphrey can understand human language, he can’t understand the frog. Over time, he learns that Og is warning him, and Og comes to believe Humphrey is always agreeing with him—whether that is the case or not. It’s always fun to write about their relationship.

What compelled you to give Og his own book?

The idea to do a book from Og’s point of view came to me, and to Susan, early on in the series, but Susan felt that it wasn’t time yet—that Og had to be more established. In recent years, I’ve received an increasing number of emails and letters from children asking for a book from Og’s perspective, saying, “We want to know what he is thinking and what he has to say.” I realized that I had no idea, since when I’m writing Humphrey, I feel like I am Humphrey! But Susan and I both agreed it was time to hear from Og, so I began thinking about his point of view and decided to give it a try.

Before you began writing children’s books, you worked as a writer in the advertising business and then wrote for children’s television. How did those experiences inform your fiction writing?

In advertising, you don’t have the luxury of time to develop an idea—things have to be short and snappy, and written quickly. There can’t be a lot of extra padding, which is also true in TV. I’ve been told that my books have the feel of a script, and it’s true that as a novelist I definitely think in terms of scenes rather than chapters. In animation, you have to keep the action moving or it gets boring. So I don’t do lengthy visual descriptions in my books.

Did you find transitioning from TV writing to novel writing challenging?

It was a bit difficult to switch. Both have disadvantages and advantages in terms of storytelling—but then again a story is a story. Books are my first love, and I realized many years ago that I wanted to write my own stories rather than write episodes based on other people’s ideas.

Obviously you found your storytelling niche with Humphrey, given that the series has a total of five million copies in print worldwide. Did the books’ success take you by surprise?

Definitely. I don’t think anyone can plan that. When I look at the list of Humphrey books, I think, “Did I really write all of those?” It just sort of happened, and the books added up very quickly! At first I was surprised, but now I realize I was able to do a few things that added to the series’ success. One is that I wanted the novels to appeal equally to boys and girls, and that happened: it appears that the audience is basically 50/50. Also, having an animal main character allows me to deal with a range of problems and feelings. Humphrey has no racial or religious affiliations, and doesn’t have any kind of agenda. And the classroom setting really appeals to teachers and school librarians, who continue to be an important part of Humphrey’s fan base, for which I’m very grateful.

You included environmental information and frog facts in Life According to Og the Frog. What message do you hope to deliver to readers?

With this novel, I opened up a discussion about bringing animals into the classroom. I want to impress on children how dependent class pets are on us, and I hope the book increases readers’ awareness of what caring for frogs involves—they require more care than hamsters do, and they are extremely endangered. This story gave me the chance to share that information.

What’s next up for Og?

In his second story, Exploring According to Og the Frog, Og helps the kids in the class be brave. I recently finished it, and it’s scheduled to be published in July 2019. I’m really looking forward to having kids get to know Og better and to letting them see the students through the eyes of a second, very different animal. And both Humphrey and Og are genuinely kind and concerned about their human classmates. They are good models of how to get along with others—and how to be a true friend.

Life According to Og the Frog by Betty G. Birney. Putnam, $16.99 July ISBN 978-1-5247-3994-2