The natural world is full of extraordinary animals with amazing life histories. Some were surrounded by myth and misunderstandings for a very long time whilst others have only recently revealed their secrets. How did two very small animals from opposite ends of the world send shockwaves through the scientific community and upset the reputation of leading scientists? Nature has twisted the tusk of the narwhal and the shells of snails and their relatives, but what is the purpose? Sir David shares the stories of these extraordinarily shaped creatures and reveals why he considers them nature's curiosities. Each of the fifteen episodes features two different animals with curiously distinctive evolutionary quirks, linked together by a common theme.