Platypuses

The Missing Platypus
By Ellie O'Ryan, Dan Povenmire, Jeff Marsh
"A spy mission gone terribly wrong causes Agent P to disappear! Will Perry ever make it back home? Or will Phineas and Ferb never see their pet platypus again?"--Amazon.com.
Percy the Peaceful Platypus
By Jill Morris
A baby platypus lives and grows in his mother's burrow until he is old enough to make his own, but he is caught in a flood and is in danger of dying until he is rescued by some soldiers.
Platypus: World's Strangest Animal
By Elizabeth Parer-Cook, David Parer
This book will take you on a journey into the bizarre world of the platypus and echidna - the world's only egg-laying mammals - and offers clues as to where in Australia you may go to see these intriguing animals.
Story of the Platypus
By Anita Ganeri
This series describes animals that were once thought to be myths or hoaxes.
Platypuses
By Greg Pyers
This series carefully looks at all aspects of these animals: habitat, food, adaptations, reproduction, distribution, endangered status, etc.
Ornithorhynchus (or-nith-or-ink'-us Ana-tyne'-us): The Platypus
By Pauline Reilly
Ornithorhyncus the Platypus
Perry speaks!: Phineas and Ferb

Phineas and Ferb build a "Perry translator" so they can finally understand what Perry the Platypus is saying.
Platypus Deep
By Jill Morris
When Orni the platypus goes in search of a deeper home, he discovers how important his creek has been to many platypuses over millions of years. Age 3+.