Heads up, Smash Bros. fans: the Mii Fighter DLC costume packs are now live in North America and Europe. You can grab your Mega Man X or Proto Man duds for a single platform for $0.75 a pop, or get Wii U/3DS bundle for $1.15.
To access this content you'll see a new eShop icon in the game. Simply press the Y button and you'll be directed to the eShop. After making your purchase the game will restart and the content will be unlocked. If you purchased the bundle pack you can view your 3DS download code under My Menu --> Account Activity. It will be in the receipt.
Have at it!