Captain Toad: Treasure Tracker is Almost a Zelda Title
Shinya Hiratake, the director of Captain Toad: Treasure Tracker, envisioned a game set inside of smaller worlds. By removing the jumping from a platformer, he reasoned that the levels could be a lot smaller and more compact. Originally, Hiratake thought that such a mechanic would have no place within the Mario universe, due to most of the characters in Mario having the inhumane ability to jump incredible heights.
The director and his team managed to scrap together a small tech-demo of this idea, starring The Legend of Zelda protagonist, Link. Link was the perfect option, as anyone who has played a Zelda game would know that Link has an inability to jump unless he walks right off of an edge.
When presenting the idea to the higher-ups, Hiratake actually reports that:
"Mr. Miyamoto asked us how we were planning on bringing these diaramas into production. He thought we were pitching him an actual product design."
That means they must have done surprisingly well.
Alas, Link was not meant to star in a compact puzzle/platformer, and the idea was quickly shot down. However, Miyamoto offered them the chance to add their design into the upcoming Super Mario 3D Land as a mini-game. This means that the team had to find a new star (because exceptions like Link appearing in Mario Kart 8 are definitely not made lightly).
Hiratake remembers seeing a certain Toad appear from Super Mario Galaxy that always carried around a backpack. Well, with a backpack on their back, a Toad could not conceivably jump at all with those stubby little legs.
After Super Mario 3D Land had a successful release, Miyamoto approached the team and requested that they make a full-fledged title out of the adorable, little minigame. And thus, Captain Toad: Treasure Tracker was born!