Sector 7 by David Wiesner
A small cloud and a boy become friends on the observatory of the Empire State Building. The cloud takes the boy flying in the sky - to Sector 7, a kind of dispatch center for clouds.
The small cloud and his friends sneak the boy into Sector 7, avoiding human-looking workers at the check-in station.
The workers at Sector 7 give all the clouds their assignments and send them off. But, the clouds are not happy with their assignments. They are told to assume stereotypical fluffy cloud shapes (shown on blueprints given to each cloud). The clouds show the boy some other shapes they prefer: three-dimensional stars, block like cube designs, and swirly spheres.
The boy draws them new blueprints - in the shapes of tropical fish and other aquatic creatures. The Sector 7 workers notice, and try to make the clouds take on the fluffy shapes they were assigned. The Sector 7 workers find the boy and send him back to the Empire State Building. The small cloud follows, and stays with the boy.
When they leave the Empire State Building, they see that the sky is full of big clouds in interesting shapes - aquatic creature shapes.
Enjoy the creative clouds, the full-color illustrations, and the story of friendship between the boy and the small cloud.