The Wii U GameCube controller adapter is now available for pre-order on GameStops's website, and it comes with a Wii U GameCube Controller.
The package will run you $49.98, and is expected to arrive at your home by May 1.
The Wii U GameCube controller adapter was released alongside Super Smash Bros. Wii U and is only compatible with the brawler.
It was originally thought the adapter would be compatible with all games in which the Wii Classic Controller, Classic Pro Controller and Wii U Pro Controller could be used, due to a listing from Nintendo.
The company later stated the listing was an error and replaced it with the correct information.
Thanks, Nintendo Life.