Known as Atsumete! Kirby in Japan, you take control of not 1, not 2, but what looks to be up to 7 (maybe more) Kirbys at the same time. From the trailer, it looks like you control them via the touchscreen. You can attack, jump, or direct the little marshmallows by tapping, draggin and flicking the touchscreen using the stylus.
I'm glad to see that Nintendo is still giving the DS some love by releasing new games for it. To all you 3DS owners, don't forget that it's backwards compatible with DS games.
Kirby Mass Attack is schedules for release on September 19, 2011 in North America.