Imagery of loneliness
Mr. Popper is depicted as a person who doesn't line up with the expectations of the people in his community, so he feels isolated, like a pariah. Over the course of the movie, that problem only worsens, because his care for the penguins is such a strange course of life that the community really doesn't understand him. When he makes an honest mistake, the community is unforgiving, and his punishment is jail time, where is alone again.
The cold imagery of survival
The penguins introduce imagery all their own, bringing Arctic temperatures with them (when he has to build them a cold habitat), and since they are poorly cared for by their original owners, he has to avidly create a chance for survival. In the end, he fosters a flourishing penguin family. His reward is that he gets to travel with his penguin family to their habitat, to North Pole, where he himself will be asked to survive.
Adventure as problem-solving
Although he doesn't get the adventure he's always wanted (until the very end), Mr. Popper endures an emotional journey by problem-solving each day as the penguins complicate his life again and again. The constant headache is something he endures privately, without community support, so in a way, he is in an adventure all his own, because no one really understands the drama of his own story but him. It's as if he has departed his community into the wilderness.
Imagery of society
The jail, the interrupted symphony, and the conductor are all imagery pointing the reader toward the authority of social normalcy. By asking Mr. Popper to fit in and fall in line, they overlook the wonderful mystery of his life and his point of view, and they ignore the spectacular serendipitous nature of being randomly visited by penguins. Their confusion and fear and prejudice is depicted through hubbub and chaos.
