Mario was not a character that was content with sitting on his laurels when it came to adventuring around the gaming world. Mario has been a doctor, kart racer, played many sports and of course has championed the saving of a couple of different princesses. The only thing he hasn't really done yet is actual plumbing of any kind. Mario has even entered the turn based role playing games with Super Mario RPG with a little help from Square Enix (one of the few companies allowed to work with Mario characters in an official manner).
Here, Mario is still trying to save a princess (ugh) but this time the festivities take place one battle at a time and you have to take turns with the enemy. The first thing that you are probably thinking about this is wrong, the game actually works. This proves there is a decent amount of depth in the Mario games, just we are conditioned to them being action platformers more than anything. It also proves Nintendo knows how to expand the Super Mario franchise to even more genres than thought possible (kart racing, doctor, puzzle, etc). Pitting Mario and company in a role-playing game is probably the last thing fans thought would occur when first inserting that Mario Bros cart in their Atari console, or Super Mario Bros into the Nintendo Entertainment System.
Super Mario RPG takes the Mario universe in a new direction and sadly, Nintendo has not revisited it since. There have been "quasi" sequels over the years but nothing directly related. Super Mario RPG has the distinction of being the last Square Enix game for a Nintendo platform till 2002.
Super Mario RPG has been released on the Wii Virtual Console but that is it as far as re-releases. For physical carts, it is either eBaychecking Amazon
.