From 3/25 to 4/27 2016, you can head to GameStop or Best Buy, or go to Amazon.com and buy an amiibo to get a free download code. Use your download code on Wii U and you can get early access to Mini Mario & Friends amiibo Challenge. You will need an amiibo to start the game.
Not a bad bonus if you were going to buy an amiibo anyway. Not so great for anyone who has a complete collection.