http://www.gameinformer.com/b/news/archive/2014/09/12/report-3ds-can-be-used-as-wii-controller-in-super-smash-bros.aspx

A gamer in Japan has posted a picture which indicates that the 3DS can be used as Wii U controller for Smash Bros.

Kyle McLain posted the image below, along with the tweet: "Am I crazy, or does this say that if you connect your 3DS with your Wii U, that you can use your 3DS as a controller?"

Several users confirmed this translation of the Japanese onscreen text, as did IGN.

We'll have to wait for official confirmation from Nintendo to see if this is real, but it looks convincing.

That's pretty cool yo.

IDK if they're going to be good as a pro controller since The 3DS doesn't have a thumb sticks.

Shit's dope AF yo.