During an interview with IGN,[4] Takashi Tezuka, Nintendo's analysis and development's general manager, stated that multiplayer for Super Mario Galaxy is more likely to be co-operative. Two-player functionality was already confirmed for the game. The development team is already experimenting with new ways to use the Wii Remote so that one player can control Mario while the other aids him. Conversely, Miyamoto also suggested that the second player could have the ability to interfere with Mario's progress. This is great news to me. The last co-op was Mario World right? and it alternate. Am I late has this news been out?

We've actually known this for some time. The way it works is that a second player can be given Wiimote pointer duty. As seen in gameplay, the pointer has a star icon on screen. That icon can be used to grab items out of the air, activate switches, launch catapults and grab and slow down enemies. It won't be a two player game in the traditional sense of both people playing the game the same way, but it sounds like a really cool way to make it a sort of 1.5 player experience, in that a second person can just jump in, help the main player along (or really get in their way), and jump out at any time.