Nintendo did not introduce the classic controller for the Wii at their press event, but it showed up on their Japanese Wii site.

This controller makes a lot of sense, as the Wii has a virtual console and can play old Nintendo games. The classic controller has all the buttons and controls to play those games traditionally.
Looks like it is only planned in a wired version as of now.
More details on the Japanese Nintendo Wii site (Japanese).

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