Wii U:
This controller is only compatible with Super Smash Bros.™ for Wii U, and cannot be used with any other Wii U software, or with Wii software on a Wii U console.
Wii:
Compatible Wii software will display one of the icons above [GameCube Controller Icon] on its packaging, or on the Wii Shop Channel for downloadable titles.
[Transcribed from the back of the case.]
Additional Specifications
To play Super Smash Bros. for Wii U with a Nintendo GameCube controller, you will need the GameCube Controller Adapter for Wii U (WUP-028), sold separately.
Bundled Accessories
Nintendo GameCube Controller (DOL-003) - black x 1