Does Wii games work on the Wii U?

Yes, the Wii U is fully backward compatible with Wii games, Wii downloads, purchased WiiWare and Virtual Console games and has the Wii Menu built into it. However, Wii games cannot be controlled with the Wii U GamePad and will not be displayed in HD on the Wii U console.

Also, GameCube Contollers will not work on the Wii U even if the Wii game allows the use of GameCube Contollers. There are GameCube Controller Adapters (Mayflash) that were created that the GameCube controller to function like the Wii Classic Controller, but is not an official product of Nintendo.