If you visit Google today, you will notice a very interesting Google Doodle. The Doodle is designed to honor H.G. Wells, whose 143rd birthday would be today. Who is he? He wrote the 1898 classic, The War of the Worlds and is often referred to as "The Father of Science Fiction."
Here is the logo:
What is unique about this logo, compared to other logos is that Google had two previous logos leading up to this one, kind of hinting that this was coming.
The first was the missing O Google logo:
The second was the missing L Google logo:
The logos themselves did not hint to what was coming, but with aids from Google's Twitter account, @Google, some people were able to crack the code.