Go ahead, search Google for [zerg rush].
That is the latest easter egg, a Star Craft component, where these zergs rush to attack you and you click on them to kill them off. You can now play the game on Google by clicking on the Os to protect the search results.
When you lose, it builds GG using the Os that attacked you. GG is a classic component to the game, it means Good Game.
Here is a video of a real Zerg Rush explained by an avid player:
What a voice!
Here is the GG:
Here is a video of me playing the game, I am not too good: