May not be the hottest deal ever, but may help someone.
When you register Mario Kart 8 (game) before 31/07/2014 you can claim a free download for one of these titles:
New Super Mario Bros. U
Game & Wario
The Legend of Zelda: The Wind Waker HD
Sonic Lost World (Wii U version)
Mario & Sonic at the Sochi 2014 Olympic Winter Games
Wii Party U
The Wonderful 101 (PEGI 12)*
Monster Hunter 3 Ultimate (Wii U version; PEGI 12)*
Also it should work if you buy the game itself, I got the bundle so bundle it is.
Here is the link to T&C from Nintedo www:https://www.nintendo.co.uk/Campaigns/Mario-Kart-8-Bonus-Game-Promotion/Terms-Conditions/Terms-Conditions-879237.html