Need a hand, Luigi?

On each occasion that we've played Luigi's Mansion: Dark Moon, the demo on offer has been a single-player level. The prospect of multiplayer arrived before promptly disappearing way back in November 2011, with Nintendo listing multiplayer as a feature, before saying it was all a big mistake.

Yet now we have the official site for the game, and at the time of writing it says the following.

With so many new places to explore, all new ways to capture ghosts, and a brand new local multiplayer mode, Luigi's Mansion: Dark Moon is another star turn for Mario's heroic brother—and it's only on Nintendo 3DS.

Curiously, the info side bar shows "No. of Players: 1 player". Does anyone at Nintendo know for sure whether there's multiplayer in this game?

We're going to assume that local multiplayer means more than StreetPass data exchanges, as descriptions normally specify when that feature's being used. What could this multiplayer be? Do two Luigi's compete to clear a room quickly, or is one a ghost and another Luigi in a twist on the mascot's appearance in Nintendo Land?

Right now we don't know what the mode is or whether this is another listing error. Until we know more, wild speculation is welcome in the comments below.

Thanks to Joey Cummens for the tip.