While Captain Toad had his own mini-game in Super Mario 3D World, Shinya Hiratake, co-director of the upcoming Captain Toad: Treasure Tracker, actually envisioned the game's concept as part of a very different Nintendo series: The Legend of Zelda.
Hiratake reportedly liked the idea of a platformer that focused on puzzle-solving and outlawed jumping altogether, but couldn't imagine any Super Mario characters being unable to jump. Link from The Legend of Zelda series, however, seemed a perfect fit.
The team showed a tech demo to Miyamoto, who shot the idea down as a Zelda title, but incorporated it as a mini-game in Super Mario 3D World, using Captain Toad (weighed down with a heavy backpack) as the star. Now Captain Toad is getting a whole game devoted to the diorama-like treasure hunting antics, leaving us to imagine how the game might've looked had they stuck with the Zelda theme.