No, it's not some under-the-radar new game -- IGN has gone and written up a fairly detailed review of the cardboard box Microsoft sends for you to mail in your broken console for repair:

By coffin, we mean a cardboard box. But this is no ordinary cardboard box from Microsoft as this cardboard box comes with another cardboard box inside of it, and inside that cardboard box is a set of instructions for returning our lifeless Xbox 360 to Microsoft for repair. The box was shipped to us via UPS 3 Day Select, and comes packaged with a return label that should carry the box back to Microsoft with the same swift delivery. The cardboard box, the instructions, and the return shipping label all come free of charge from Microsoft.

Their final verdict? A respectable 7/10, though personally I would have scored Gameplay a bit higher than their 4/10 ("It's a box.") I had plenty of fun with boxes as a kid. You know, before I got my Super Nintendo.