Want to hear a tangentially related tale?
My dream Mario game is a sort of multiplayer Mario-and-Luigi style RPG for the Wii U set eighteen years after the Mushroom and Koopa Kingdoms have made peace. You play as Mario's daughter (hereafter called Mary because the concept alone drained my imagination) and her friend, Bowser Jr. The princess has been kidnapped, but so have Bowser and Mario, by a completely new enemy. You know how Miyamoto said the Koopalings weren't Bowser's sons? Well, their real father, who logically must be called Morton, is the perpetrator of this crime, and it's up to you to save your parents.
As you travel across the vast lands, you'll pick up two extra playable characters: the geeky daughter of Daisy and Luigi (hereafter known as Lewis), and the new chief of the Yoshi Tribe. Mary, Bowser Jr, Lewis and the Chief all have different abilities that will come in handy on the journey: Mary can use powerups and manage the inventory of items, Bowser Jr can use his claws to climb walls and melt things with his fire breath, Lewis is technologically minded and can shoot switches far into the distance with his lasers, and the Chief can use his long tongue and flutter jump to cross large gaps. With every district the quartet of adventurers enter comes a new obstacle that affects one of the players, forcing the other three to work together to help their friend across. For example, in the tropical district, Lewis is unable to enter bodies of water due to all the electrical items he's carrying, so Mary and Bowser Jr have to build bridges for him. (But not the Chief, because the tropical district comes before the forest-filled Yoshi Island where the Chief joins the party.)
The multiplayer aspect comes from a drop-in playstyle compatible with the Nintendo Network. It's sort of like Left 4 Dead, in a way. Players can choose to allow online players to enter their game and control one of their teammates, or enter another player's game themselves, so long as they've cleared the world that the host is up to. (Because spoilers are bad.) With multiple players, solving puzzles and choosing moves in combat goes by much quicker due to the fact that the host player doesn't have to control everyone.
But since Nintendo will never, ever make a game like this, I don't know why I brought it up.
So... carry on.