Happy Aquarium's arctic theme brings all the bears to your tank
So how do you get these bears? Well, while the demo tanks are suppose to function as stores, it seems that clicking on the bears in the tank won't get you a "Buy" prompt. The bear cubs are currently an exclusive lost item, so you'll have to count on your friends to share their sightings on their Walls.
But a bright-eyed, ears-wiggling, baby Pink Polar Bear is available at the in-game store for 48 Facebook Credits or 58 Pearls. She's got a maturation rate of 72 hrs. and can be mated with the normal Polar Bear.