How Back-Back Got His Name by Thomas Weck and Peter Weck, illustrated by Len DiSalvo

From chapters.ca:
After Plumpton the opossum loses his back, Lima Bear and his clever friends become detectives on the search. They try new and different ways of thinking in order to try and solve the mystery- even having to band together to protect each other in times of danger. The primary concept presented in the story is that the tolerance of differences in others yields benefits.