Update, whilst indeed something happened on Saturday news fro m the twitter page of Surgeon Simulator is that this had nothing to do with the puzzle, from a comment in a thread on popular social site reddit.com they also mention that the puzzle will be ongoing with an "update in the coming weeks"
Surgeon Simulator 2013, a darkly humorous and quite often over the top operation simulator has been causing quite a stir recently. Recently Surgeon Simulator had a DLC release which as well as changing the main characters of the game, Nigel is replaced by the Medic and Bob is replaced by the Heavy, included a little puzzle on the base of one of the items in the game, which included a depiction of the solar system and some characters written in Korean.
Now this would normally not be too much of a big thing, but earlier this week a patch for the classic Half Life 2 made the game default to the Korean language, so immediately people have started tying this up to being a new Valve ARG (Alternate Reality Game) of which there are many previous examples.
The puzzle has even been commented on by the official Surgeon Simulator Twitter account adding more fuel to the fire.
Although ValveARG.com are not yet calling it an ARG labelling it "not actually an ARG but just a puzzle" they have also released a document on the current status of it and you can get the latest up to date info from the chat app on their site.
Although current thinking is that it points towards the start of the Summer Sale.