Ratchet & Clank: All 4 One introduces four player co-operative gameplay, allowing players to team up as Ratchet, Clank, Qwark and Dr. Nefarious. Helping our heroes (and the Galaxy’s most notorious villain) take on their biggest challenge yet, the missions takes place on a mysterious world with an arsenal of over-the-top weapons at their disposal.
We find the heroes in the midst of a dilemma of intergalactic proportions when Dr. Nefarious’ latest evil plan goes awry leaving Ratchet, Clank, Qwark and Nefarious himself caught in the snare of a powerful and mysterious machine. Begrudgingly, the Galaxy’s biggest do-gooders and its most sinister criminal must work together to discover a means of escape.
That's all we know so far, but the announcement of the game has also come accompanied with some screenshots...