It's called Santa Claus vs. the Snow Monsters, and the premise is that Santa has crash-landed in the snow on Christmas Eve, and has to fend off an army of snow monsters bent on finding out if that belly actually tastes like a bowl full of jelly.
The game is controlled with a dance mat (like in Dance Dance Revolution), and you control Santa inside his hastily-constructed snow fort. He can rotate left and right to face the oncoming snow monsters in different directions, he can duck their belched-out snowballs, and throw snowballs back at them. I'm doing the programming and Matt is doing the artwork. (That's not Santa in the snow fort there, obviously - that's a pirate from our pirate game that I'm using as a placeholder graphic for Santa.)