Google's running a special logo for Halloween, as is tradition. Last year, a bunch of Googlers, from the doodle team but not only, got together to carve humongous pumpkins to make up the Google letters and the doodle was a timelapse of that.
This year, Google is going for a more traditional approach, with an interactive animated doodle. All you have to do is click around and discover all the secrets, not that they're so hidden.
Each door opens to reveal one of the ghostly Google letters, well the second one has two letters, technically. There are also a few other things you can click on, the crow, the trash can, the spider.
Overall, it's a cute doodle and a fitting one for Halloween, but it's not going to win any prizes. It's done in CSS3 and seems to be using Web Audio API for the sound, so it only works in Chrome.