The game sounds like it should be an April Fool's joke, but Goat Simulator is real, and coming out via Steam on April 1st 2014. The game can already be pre-ordered from developer Coffee Stain Studios.
Goat Simulator was made during a small game jam at the studio (where programmers try to make a game in a limited time), but a YouTube video of game footage became a bigger hit than any of the Coffee Stain Studios' game trailers. The studio decided to go ahead and make the game, on the back of a wave of media and gamer interest.
Goat Simulator will not be a very complex or serious game, as the creators say they want to keep it simple. It will feature an exploding gas station, a low gravity facility, a water park and a breakable Stone Henge, among other things. Steam Workshop will also be added to the game, to allow users to add 'mods' to the game, as they do with The Elder Scrolls V: Skyrim and others.