Warning: Wikipedia contains spoilers
The story takes place in contemporary Japan, where a group of Tanuki (Japanese raccoons) is threatened by a gigantic suburban development project outside Tokyo cutting into their forest habitat, terraforming and dividing their land. The Tanuki are portrayed as a highly sociable, talkative species, able to use "illusion science" to transform into almost any visual appearance.
The Tanuki begin fighting for the diminishing resources of their habitat, but then decide to unify against the humans to stop the construction. Using their illusion skills, they stage a number of diversions, culminating in a "ghost parade" to make humans think the growing town is haunted. When all efforts fail, in an emotional scene they stage one last grand illusion, temporarily transforming the urbanized land back into its pristine state.
Their strength exhausted, the Tanuki most trained in illusion are left with no choice but to abandon others, disperse and blend into the human society. One day Shoukichi, one of the Tanuki, is coming home from work when he sees another Tanuki running toward a golf course to meet his companions. Overjoyed, Shoukichi transforms back into a Tanuki and joins in the gathering.
In an emotional final scene, Shoukichi addresses the viewer, asking humans to be more considerate of Tanuki and other animals less endowed with transformation skills, and not to destroy their living space.
Although it is not among the most popular Studio Ghibli films, and is regarded as strange by Western audiences because of the theme of Tanuki using their testicles to create illusions, Pom Poko is a thoughtful, humane film which powerfully presents the themes of humanism and ecological distress.