Note: This page is based on an assumption referencing Animal Crossing: New Leaf since the Animal Crossing mobile game is not released yet. Will be updated once the game gets available!
During the event, you can play a mini game with Blanca. As rewards for the game, you can get villager's photos. This is the perfect time to collect the photos since the only time you can get one is if you have strong relationship with them or they are leaving your town.
First, you'll need to talk to Blanca, the faceless cat in your town plaza. She will change herself to look just like someone in your town and visit your villagers. Enter one house and you’ll be surprised there is two identical villagers. You need to identify who is the real and the fake one. You have to give a towel to the faker to reveal its true face. If you guessed the real one, they’ll give you their photo.
Tips
It's easy to guess who’s the real one during conversations with the villagers. It might be their greatest dream, about their siblings, favorite phrase or special skill. Definitely, fake one will tell you a different thing.