Google often has fun with their name on days that they feel are special in one way or another. If you happen to hit their site on one of those days, you're treated not only to fun art like this one,
but also clicking on the image often takes you to more, related info, like this:
and it makes people like me want to read more, for example by looking in Wikipedia, like this:
So, simply by having a little fun, Google can spread culture and knowledge to those who choose to look. It's a cool idea.