Video games usually live in the digital sphere. The user interacts with a game controller and that's about it. When I saw the game Skylanders where you buy different figurines along with the game to be able to play different characters or regions in the game, I thought you could take this paradigm further:

To bring the characters back into the physical world.

I made a 2D jump 'n run game in Unity3D where the player runs through a forest and collects acorns while avoiding obstacles. The controller is a physical plush squirrel which I sewed. Inside the squirrel is an Arduino Leonardo which connects to the computer. Via a light sensor, the Leonardo detects when the user lifts the squirrel to jump over obstacles or to collect an accorn.
Unlike in Skylanders, the main characters ( = the controller) is not represented in the game. It lives in the real world alongside the player and controls the digital world.

The title is a little play on an academic paper with the title "Rubber shark as user interface".