Top ten animal companions in fiction

Django Wexler is the author of The Thousand Names and The Forbidden Library. At the Guardian, he shared a top ten list of animal companions in children's fiction, including:
Bartimaeus from The Amulet of Samarkand by Jonathan Stroud

Bartimaeus is of course a demon – specifically a djinn – rather than an animal, but he spends a fair bit of time in the form of various creatures both real and