Best Buy is currently running a special promotion for anyone interested in purchasing Donkey Kong Country Returns 3D on the 3DS. For those that purchase a copy of the game, Best Buy is including a download code for Super Mario Bros.: The Lost Levels from the 3DS eShop. At this time it appears that only the physical copy qualifies, even though they list the digital download code option for purchase as well.
If you were planning on picking this up, a free bonus game never hurts. Make sure you act fast, as this is likely a limited promotion.
You can navigate to the deal on Best Buy’s website here: BestBuy.com