Called a Google Doodle, it refers to the special artwork created to to appear on the main Google Search page. In this case, the image honors Tanaka's 213th birthday on October 16, 2012.
So... what's so important about Tanaka? I'll give you the basics, and will do a more in-depth presentation soon enough.
I came across Tanaka while researching Japanese automatons and clocks a couple of weeks ago —both of which are so mechanically complex it boggles MY mind... and I can take a watch apart and put it back together again (though I do have issues with my old flashing VCR).
Known as the "Thomas Edison of Japan", the Google Doodle shows a karakuri (automaton) inking the Google logo with a calligraphy brush.
As mentioned, along with the karakuri, Tanaka also created something called the Myriad Year clock in 1851. This one deserves it's own category as well, but let's just say it shows the time in seven different ways (because one way is not enough for the Japanese - sarcasm), and contains over 1,000 parts making each one himself with files and saws over a three-year period. Hopefully he charged a lot of money for clock listed as Item #22 in the Mechanical Engineering Heritage.
Other cool inventions from Tanaka include Japan's first steam locomotive (I'm a model railroader, too) and Japan's first steam powered ship and a paddlewheel ship. (I've seen ships!). As well, he created a loom (I built my own looms when I was 8-year-old and made pot holders and scarves!).
While obviously not in the same league as this man, I am impressed with his achievements, as was Google.
Oh... by the way... his first company... it's part of what is now known as Toshiba. (I have a Toshiba TV!)
Anyhow.. here's a YOU TUBE video of the Google Doodle of Tanaka Hisashige: