Surprise! Mario Maker is indeed a real game that lets you build your own Super Mario Bros. stage, stop while building it, and play your creation. While rumorssuggested the creation game would be coming to Nintendo 3DS, it's in fact a Wii U game.

The game arrives in 2015 in Europe and North America, and will allow players to create Mario stages using graphics from either the original 8-bit Super Mario Bros. or in the style of New Super Mario Bros.

http://www.joystiq.com/2014/06/10/ma...-1-1-on-wii-u/