Recent 3DS release Steel Diver has had a long, long road to release: starting out as a DS demo back in 2004, the title eventually wound up on 3DS, but it could have been released much earlier if its original course had been followed.
A recent Iwata Asks article focuses on the 3DS sub title, with producer Tadashi Sugiyama revealing the original intention to release the game on DSiWare:
We began by making the game DSiWare, but we thought it had more potential to be something even bigger, so we decided to make it packaged Nintendo DS software for sale in shops. To that end, we began considering the addition of other modes.
That wasn't the only big change the game went through: originally Takaya Imamura wanted the game set in a very different universe to its current incarnation:
I thought it would be fine to set the game in a flashy, glittery world like—and I'm not kidding—a submarine version of Mario Kart. But Sugiyama-san said, "No".
Eventually the game was fleshed out to its full form without a homing blue shell in sight. You can read more about the game in our Steel Diver review.