When your favorite villagers show up in your dreams. Not in dream towns, but in your actual sleeptime dreams.
Also, when you've memorized most conversations of your favorite villager types, and become really happy when seeing a slight variation that you didn't know existed.
Every time you see E3 news, leaks, announcements, you automatically anticipate that it is Animal Crossing Wii U and you fan girl like crazy when any videos on YouTube or posts on this forum are related to Animal Crossing Wii U.
When you begin to think that there should be an Animal Crossing: OCD Edition for all the people that go cray trying to prevent their villagers from changing anything ever
When you fall asleep with your game on while Two Days Ago is playing and you get this creepy dream while you're still hearing the song, then every time you hear it afterwards, you get sp00ped