Super Mario 64 DS

Super Mario 64 DS is a three dimensional platformer launch title and remake of the original Super Mario 64 for the Nintendo DS, most notable for adding minigames, 3 new playable characters, 30 extra power stars, new levels, and improved graphics. It's regarded to be one of the best games for the DS, Selling 11.06 Million copies worldwide.

Similar to the Nintendo 64 version, the game starts with one of the 4 protagonists, Mario getting a letter from Princess Toadstool inviting him to her castle for cake. Arriving with his brother, Luigi and arch-rival, Wario they head to the castle and enter it. The crew split up and enter different painting worlds to then be captured and trapped in the walls by their arch-enemy, Bowser. After a long period of time has passed, Lakitu wakes up Yoshi to inform him that Mario hasn't returned yet. From then on, Yoshi must unlock the castle and journey to save Mario, Wario, Luigi, and Princess Toadstool by entering the many paintings that lead Mario and his crew to levels so they can collect as many stars as possible, while freeing Toads from the castle walls.

Cut Concepts
Some cut concepts and ideas from the original Super Mario 64 such as Luigi and Yoshi being playable made it back into Super Mario 64 DS, most of which were thought of in 1995-1996.

Earliest builds
A demo of one of the most earliest known builds of the game was playable at E3 2004. In this demo players would choose from a menu on the touch screen where they could choose different painting worlds, most of which seem to contain a different picture from the final game. Another menu for multiplayer where you could choose between the 4 could appear upon starting the DS. In single player, the touch screen allowed for switching between the 4 characters as opposed to entering different character rooms in the final game.

Showcased at the same E3 was another demo titled "Mario's face", where the player could use a stylus to stretch Mario and Wario's face, and even make it 3D or outlined like a cartoon. This build is clearly what ended up being Mario's face in the title screen of the game.

Phenomena
Discovered and theorised recently, every copy of Super Mario 64 is personalised. Nintendo implemented an experimental procedure into Super Mario 64 which slightly alters the game to suit the player whose playing it, which is why some players report that there's always something off when playing somebody else's copy of Super Mario 64. It's unlikely that Super Mario 64 DS shares the same personalisation algorithms as its Nintendo 64 counterpart, as the game was not built off of Super Mario 64 like many assume. Because of that, it's likely that the Personalisation A.I. does not influence Super Mario 64 DS.

Waluigi
Upon its release, Waluigi was highly speculated to be playable in Super Mario 64 DS, finishing the set of 4 plumbers in-game. The fourth key door outside the Rec-Room was the liekly source of this belief, although all it contains is a star, and when entered after gaining the star will scare off the player with the laughter of Boos. This can be unlocked with the key obtained by catching all the shiny white rabbits. Despite that, many still believed that Waluigi was intended to be in the game and his existence has acted as Super Mario 64 DS' most talked about rumour.

Several rumors and fake images were created around Waluigi, most famously the Purple Prizes rumor. This fake newsletter claimed that Waluigi could be found by being the "fastest foot-racer in the land" and defeating the secret "Rabbit king", and only then will Waluigi be playable. However, this was an April Fools joke orchestrated by DeviantART user King-Bowser-Koopa.

Trivia

 * With some personalised copies of Super Mario 64 featuring Luigi or even Wario as playable characters, it's possible that Super Mario 64 DS is based of a heavily personalised version of the original Nintendo 64 game.
 * It's likely that Mario 64 inspired the creation of the Nintendo DS, which is why it's more powerful than the Nintendo 64. This could also be why some players say the personalisation occurs more-so on the DS versions of the game.