I hope you weren't planning on playing the newly announced Zelda: Triforce Heroes co-op locally with just one other person because you can't!
While bumbling through Kotaku, I discovered more promising news from the house that Mario built. The new co-op focused Zelda game can't be played with just two people (unless PVP Zelda is your thing). The journey must be taken solo (with two straw dummies in tow) or with two human dummies in tow. The Four Swords games didn't have this issue.. I guess I should try to force someone I know to buy a 3DS and this game or bet our success on a random.
Source: Kotaku