COEUR d’ALENE — Ten years after they began a hide-and-seek game in downtown Coeur d’Alene, Mudgy & Millie’s new adventure will be revealed Sept. 8 at the annual birthday celebration for the pair at Coeur d’Alene Public Library.

The fun begins at 11 a.m. in the Community Room when author Susan Nipp will read the new book, “Mudgy & Millie Adventures: Australia” and share a new Mudgy & Millie song.

The new story is illustrated by Charles Reasoner, who created the art for the first book back in 2008. He will be at the upcoming party along with sculptor Terry Lee.

The book is the first of a planned series that will take the moose and mouse to different countries around the world in their hot air balloon. Copies of the book — in both hardcover and paperback — will be available for purchase and signing on Sept. 8 by Susan, Charles, and Terry at the birthday party.

Participants are, of course, invited to bring copies of the original “Mudgy & Millie” for signing as well.

As with all previous birthdays, the Mudgy and Millie characters will be there, too, and The Coeur d’Alene Resort bakers will provide birthday cake.

All royalties for “Mudgy & Millie Adventures: Australia” will benefit the Coeur d’Alene Public Library Foundation. The original book has sold more than 27,000 copies through six printings and has raised nearly $150,000.

Nipp said the new book will also be used to encourage reading by children of all ages.

Copies are being donated to schools in the Coeur d’Alene School District by Figpickels Toy Emporium — the publisher of Mudgy & Millie books — the Coeur d’Alene Public Library Foundation, and Charlie and Susan Nipp. An online teacher/parent guide is being added to the Mudgy & Millie website: www.mudgyandmillie.com.

Reasoner and Nipp will be visiting eight local schools the Monday and Tuesday after the celebration.