In case you don't know, LocoRoco as a series is a charmingly adorable platformer that is controlled by tilting the world with the L and R bumpers on the PSP. Tapping both causes the fat, bloated LocoRoco to bounce, and you'll have the option to break up your LocoRoco into cuter, smaller LocoRocos by tapping a button.
LocoRoco: Midnight Carnival breaks things up in two ways: first, this game is themed around Halloween. The levels take place at night, and there's pumpkins and stuff. It's cute, and ties nicely with the late October release.