When current Nintendo president, Satoru Iwata, first joined the company, he looked at a list of games in development for the Gameboy Advance. Noticing little Mario support on the list, he suggested to Mario creator, Shigeru Miyamoto, that they address the issue.
This is how the Super Mario Advance series came to be. The series originated as a project with the goal of adapting older Mario games for the GBA, under the care of Hiroyuki Kimura, and saw the release of Super Mario Bros. 2, Super Mario World, Yoshi’s Island and Super Mario Bros. 3 on the GBA.
After the advent of the Nintendo DS, Kimura thought to produce a "Super Mario Advance 5" on the system. Ultimately, this game was conceived as New Super Mario Bros., of which Kimura was producer. As soon as development of the game was completed, Kimura moved on to New Super Mario Bros. Wii.
This little fact comes from yet another Iwata Asks session celebrating Mario’s 25th anniversary. This interview sees Iwata talking to other Mario game developers over the years, including Yoshiaki Koizumi, director of Super Mario Galaxy.
At one point, Koizumi happily demonstrates for everyone how, during the development of Super Mario 64, Miyamoto once sprawled himself out on a desk and began demonstrating Mario’s swimming animation for him to observe.