In an interview with the venerable Japanese gaming magazine Famitsu, 3DS group manager Hideki Konno revealed a very surprising fact: the hardware project that became the 3DS did not originally include 3D technology.

Konno said, "The first time I heard from [Nintendo president Satoru] Iwata and Miyamoto about this was just after I wrapped up Mario Kart Wii and got started working on DSi Sound. They showed me this piece of hardware which later became the 3DS and said, 'Here's what we're working on right now.'"

He then revealed that the unit did not have 3D at that time: "I became involved with development starting in 2008, but at that time, it didn't have 3D visuals...With this system, you could say the timing was just right for us. It was the right time to start thinking about using the latest in high-tech and try out glasses-free 3D. The technology we got to demo was really impressive, and starting in early 2009, we began to think that it was time to bring it to games."

He also told Famitsu that the motion sensors and gyroscopes in the 3DS were added to the handheld late in the development process.

Source: 1UP