Google has a long history of making special logos to go along with special days: holidays, birthdays, exploration, important stuff.
Recently, Google has come under fire for a lot of things, but in the last few days that actually made some mistakes that go against their own stated goals. Threadwatch has pointed it out more than I can, but the first result for some searchs is the Google SERP itself. That's just a mistake - why do I want to see the page that I'm currently visiting in the search that I do?
Egg On Face