Masato Kuwahara, project leader of the Nintendo DSi Hardware group, has a storied history of crafting new hardware prototypes, including a good amount of portable Nintendo game machines that never saw the light of day.
Included in those is the unreleased, dual-card capable Nintendo DSi, a hardware design that was rejected at the near-final stages of development. As Kuwahara explained at both GDC and to Nintendo president Satoru Iwata, reception to thicker, dual-DS slot device was largely negative.
The inspiration behind the two card version of the Nintendo DSi was born of the company's shorter session, more "non-game" type software. The thought process was that DS owners would want a game like New Super Mario Bros. to complement their copy of Brain Age.
Kuwahara also showed off one of the first touchscreen-ready pieces of Nintendo hardware, a Game Boy Advance SP featuring a touchpad.
Obviously, this is little more than a prototype. Kuwahara had showed earlier an even more hacked together Game Boy, one that used hand-wired connections to a Game Boy Camera, an extremely early version of the camera-equipped Nintendo DSi.
Kuwahara explained the hand wired version, built during his spare time on the weekends, wired wired in the "yakisoba" fashion, referring to Japanese noodles.
The Nintendo hardware designer also showed an early version of the Game Boy Advance. Which was huge. (And blurry!)
That fuzzy object to the right of the colour LCD equipped pre-GBA is a Nintendo DS, to give one a sense of scale.