“…I mean, seriously, there’s all manner of new interactions with the NPCs, or have you not played hide-and-seek yet? And the multiplayer is much more robust than in previous Animal Crossing games. Have you noticed that the villagers don’t all run and hide indoors when strangers are around? I’m so proud that they got over their stranger fear.” – Rich Amtower, member of the localization team at Nintendo’s Treehouse

“Because there are so many small elements that come together to make Animal Crossing what it is, it’s easy to think that this is the same game. But once people pick up the controller and experience life, they’ll see how different it is. The aspect of communication or interaction was really enhanced in this version — not only when it comes to visiting friends over Nintendo WFC but also interacting with friends over WiiConnect24 by sending letters and photos and participating in the auction in the city.” – Reiko Ninomiya, member of the localization team at Nintendo’s Treehouse

The only difference I see between Animal Crossing Wii and DS is the city and Wii Speak. The city isn’t really anything that great, and Wii Speak is the main reason I bought the game. Don’t get me wrong Animal Crossing is fun, and you get to transfer your DS version over, but there is not really anything new to it.
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