For proof of how insane our patent system has become, I offer for your perusal, the Google Doodle patent.
See also this article.
Today's Harry Houdini logo is the first to appear after Google received a very interesting patent. The "Google doodle" which shall forever after be known as the 'System and Method For Enticing Users To A Web Site' has been approved by the US patent office.
I figure the prior art for this is, oh, how about the entire internet?
The doodle patent is specific to changing the top of the page (in this case the logo) for users to see when some special occasion happens. It has prior art dating at least back to some 70s message boards.