Nintendo has applied for a patent for a “massively single-player” game. Though no specific game is mentioned, the blurb for the patent indicates similarities to an online version of Animal Crossing. The game would be played in single player mode, but actions from other players playing the same game would filter through into your game via the Internet.
An example given had one player spotting a pile of building materials in a virtual world and making a house out of it. Since the world is the same, the next player to happen along finds not a heap of lumber and tools, but a finished house (with the builder nowhere to be seen). Additionally, Nintendo’s filing suggested that one player could gossip to a non-player character in the world, who would then pass it along to other players.
“Those who want to play games that are more dynamic, not-based on Al and not-pre-scripted like multiplayer games, however, don’t want to ‘deal’ with other people, appreciate the privacy it provides.”