From the Super Mario Wiki
Ads keep the MarioWiki independent and free :)
A person of randomly chosen gender is hanging on a zip wire and the player, controlling the other of the pair, has to help him or her by tilting the Wii Remote or Nintendo 3DS left or right. This will make their partner move towards the island so they can reunite. In later levels, there will be whales (aliens in WarioWare Gold) spouting water or shooting laser beams. If the person gets caught in these, they will be sent off and the game will be lost.