The imagination is unquenchable; if it can be imagined, it can be experienced, at least by a book, anyway. A person can travel to the moon, the iditarod, or have a living room full of zoo creatures in a matter of minutes.
Many of these (above) began with a chuckle. Humor can be powerful and persuasive and possibly add ethos points to the character of the designer.
Specifically in the Superman drawings, he finds it hard to put a book down, essentially equating reading to saving the world—or a kitten.
(above) a detail of a few.