This is a peripheral which will allow you to use GameCube controllers (each sold separately) with Super Smash Bros. for Wii U.
You can connect up to four GameCube controllers using the GameCube Controller Adapter for Wii U. The peripheral plugs into the Wii U console with two USB cables. (You can use either the USB terminals in the front or rear of the console.)
You can use your existing GameCube controllers to enjoy Super Smash Bros. for Wii U with the same feeling of control as Super Smash Bros. Melee and Super Smash Bros. Brawl.
*The special Super Smash Bros. GameCube controller shown in the image is also planned for release on the same day, as well as the Super Smash Bros. for Wii U and GameCube Controller Adapter for Wii U bundle set.