The game is called Fat Princess.
It's a multi-player capture the flag game where your princess is the flag. She starts out normal princess shaped, but you feed her cake to make her larger, heavier and more difficult to capture.
Players choose classes like Builder, Archer, Knight, Wizard, and Priest to fill different combat roles.
Wow. I'm as much of a fan of inflation as the next guy on these forums, but that sounds like a terrible idea for a game. Who came up with that?