When I got Animal Crossing: City Folk in February 2015, I didn't even know that the Nintendo Wi-Fi Connection was discontinued. So I played City Folk offline on my Wii U.
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Played Animal Crossing Since 2013.
Video games are fun!
Yes, Wiimmfi works on the Wii U. I can't talk about the process of setting it up due to site rules, but feel free to google it. There are lots of good guides and videos explaining it.