Previous "Iwata Asks" interviews
have brought up several previous 3D prototypes from Nintendo, including GBA and GameCube-based versions. During his talk about the 3DS's development, hardware producer Hideki Konno revealed another prototype, designed before the 3DS was even a glimmer in Nintendo's collective eye.
Nintendo wired up a glasses-free 3D display to a Wii, and set it up on a cart to wheel around the company for demonstrations. And then, because it wasn't hacky or impractical enough, the team hooked a proof-of-concept version of the 3D depth slider to a Nunchuk -- with hot glue.