There's clearly magic in this scene, which above all strives to capture the magic of a child's imagination. Who can say they've never imagined themselves into a picture? Disney seizes upon this universal child's tendency, that even adults can recognize, to use it as a framework for his animated montage. The animation illustrates the craziness and improbability in such imaginative notions, which for some reason, allows us to accept the scene as we do. If jumping into a picture were possible- it would look like Marry Poppins, wouldn't it?
I haven't the foggiest idea about the vast and intriguing world of pavement art. In fact, I turned to an unique blog devoted completely to this subject for some superficial outside information. It's called "All My Own Work" and its devoted to the history of pavement art, especially in London. It's a very specific topic, but he does an excellent job about it, and I highly encourage the read.