Based on the book by Pierre Berton. Adapted by Kevin Kerr. Directed by Carole Higgins. A Carousel Theatre production. At the Waterfront Theatre on Saturday, April 18. Continues until May 9

It feels like Pierre Berton invited Kevin Kerr over to play and they got really goofy. This sense of shared giddiness is what makes Kerr’s adaptation of Berton’s 1961 kids’ book, The Secret World of Og, work so well.

Berton based the child characters on his first five offspring. (Two more were born after the book was written.) Their adventure is simple enough. Baby brother Paul, aka Polliwog, disappears through a trap door that has mysteriously manifested in the floor of the kids’ playhouse. Accompanied by their pets, Polliwog’s siblings set out to save him. They include bossy oldest sister Penny, giddy middle sister Pam, tomboy Patsy, and Peter, who is in love with trucks. On the far side of the trap door, they discover a magical underground world of little green people who appear to communicate all of their needs with one word, Og.

The world of the Ogs is a distorted reflection of kid culture. The Ogs have been stealing comic books and novels from above ground. They’re learning English from these sources and insist on being called names like Sheriff and Captain Hook.

In a move that will please lots of adults, Kerr takes this acknowledgment of play-acting further into meta-theatricality. Near the end of the story, one of the characters asks, “What’s the lesson?” to which Patsy replies, “I don’t know. I’m just the catalyst.” And Kerr has a great time fleshing out Berton’s characters, giving Patsy and Peter a shared delight in burps and farts. This combination of sensibilities means that Og will probably work best for kids between five and eight, and for grownups.

Patrick Pennefather has composed some swell music for this adaptation and there are some clever songs although, strangely, they’re almost all at the beginning.

Aslam Husain brings a charmingly offhand innocence to Peter, Megan Marie Gates is winningly confident—and sings beautifully—as Pamela, and Anna Cummer is perfectly pushy as Penny. I think that Marcie Nestman overacts as Patsy, but my 10-year-old companion considers her the best performer in the show.

In Alison Green’s expressionistic set, a wildly drawn tree shades the playhouse, and the playhouse sits atop a whole other world.

Act 2 sags a bit; the Ogs are obviously harmless, so the tension deflates. There are some anachronisms, too, including an emphasis on cowboy comics.

Still, The Secret World of Og makes an excellent family holiday destination.