Nintendo World Demo (Harvest Moon: Tree of Tranquility)

Marvelous Interactive's Game Panel

Marvelous Interactive held a panel at the Nintendo World convention of 2006, a convention which showcased upcoming games for the (then soon-to-be-released) Nintendo Wii console.
Game.Watch Impress reported on the showfloor panels, including Marvelous' Tree of Tranquility showcase. Mr. Katsuo Ishida of Game.Watch reported that the Nintendo World demo featured 3 interactive mini-games which allowed players to take care of the field, animals, and experience social interaction while taking advantage of motion controls and IR sensors. Below are images from Nintendo's event page and Game.Watch.

Harvest Moon Heroes

The tentative name given for Tree of Tranquility before its release was Harvest Moon Heroes. Famitsu released an article in August 2008 on the demo and the alpha build of the game. Gamekyo posted scans of these pages, shown below. The scans show concept artwork for the game, early artwork of the hero Kevin (Takeru/タケル), and images of the Nintendo World demo.
An important piece of information from these scans is the inclusion of HM64's Elli as an early development marriage candidate; a concept that was later scrapped.
This is referenced from the line, "ここは主人公の家...のはずなんだけど、なぜ家の中に女の子が!?" ("This is the hero's home...but wait, why is this woman here?!"), hinting at Elli's early development as a special secret candidate.
There is also evidence of Elli's development leftover in demo files tucked away within the main game files of Tree of Tranquility.

Demo Files in Tree of Tranquility

In the game files of Tree of Tranquility there are leftover folders belonging to the Nintendo World demo that were left behind and not removed upon release. Below are some of these files.