Final Fantasy Crystal Chronicles: Echoes of Time was originally released as a DS game. But now it's on the Wii. How did Square Enix port it over? Easily.
According to the game's director Mitsuru Kamiyama, "The DS version was the original source code, we made a system that automatically generated the Wii version." This system is called the Pollux Engine, and it seems fancy.
Even though the Wii and the DS are using the same data, the Wii handles the data differently (obviously) and renders graphics differently (ditto). Guess this means look forward to more DS-Wii-ports?