Patapon, by SCEA, is a PSP game to be released in Feb 2008. Its genre is along the line of LocoRoco, a previous successful game by SCEA.
In a two-dimensional environment, the player controls an army of miniature creatures by pressing buttons in time to create a rhythm, much like a drum would be used keep a human army marching as a single entity, or to scare an enemy.
Here is a gameplay how-to.. looks nice, eh?
Huge amounts of info, pics, teasers, videos, and themes can be found on that Playstation Portable thread by PSP_Scientist.