The PS Blog has a post by Keita Takahashi of Namco Bandai explaining in words of one syllable was PSN game Noby Noby Boy actually is.
Players control and stretch the main character Boy who, as he grows, uploads his lengths to a persistent character known as Girl, which grows at the same rate as the combined length of all the players in the world.
When she's grown enough to expand around the solar system and reach a new milestone, playable stages are unlocked for all players in the game.
Takahashi explained that he "wanted to make a game that cannot be expressed by words in the first place" and that he hopes player reaction will be, “I don’t know why, but it’s somehow interesting. I can’t stop playing.”
Sounds about right from the sound of things.
Video is through jump, and screens are posted here.