This drawing has many layers to it. On one layer, it's about the conflict between the working world and the world of raising children. On another, perhaps the child is one of the grownups, who just happens to be in a different state of mind. It's also about the two levels of existence that happen between the kid world and the grownup world, where kids' lives take place down low amongst the legs and feet, and grownups' lives take place up high in boring grownup conversations.
I'm sure there are yet more layers - like the forest formed by the legs that alludes to the forests of children's stories, and the fact the child is playing with cars while the adults commute to work.