The very end of And to Think That I Saw It on Mulberry Street perfectly captures the ultimate divide between kids and adults when it comes to silly imaginations gone wild. Marco rushes home utterly excited to tell his dad about everything that he's "seen" (even though he didn't really see it):

FOR I HAD A STORY THAT NO ONE COULD BEAT!
AND TO THINK THAT I SAW IT ON MULBERRY STREET! (110-111)

Marco is super excited about the way his mind's wandered and invented, and he's eager to share it, but he stops at the end because he realizes that his dad won't appreciate his mental gymnastics in the same way that he does. He won't see it as a wonderful thing; he'll just see it as an annoying lie. So instead, Marco just says that he saw nothing:

"But a plain horse and wagon on Mulberry Street." (122)

Marco is giving in to what his dad wants, in a way. He's giving in to the boring, ho-hum version of adult reality that his dad subscribes to, and hiding his imagination away. His dad represents all adults who are trying to repress the vivid creativity of children everywhere, so it makes sense that Marco wouldn't want to present his delightful tale to him.

But this doesn't mean that Marco's imagination is totally squashed. After all, he manages to share it with the reader of the book (yes, you) and gets his magical tale across anyway. It would have been wasted on his dad, so he gave it to everyone else.

After all, parents just don't understand.