On April Fool's Day, Blanca will come to your town and disguise herself as your villagers. The two villagers will then give out facts, such as their birthday, number of siblings, goals, etc. Blanca will always say the wrong thing while the real villager says real facts, so that is how you know it will be her. There are guides online that say the correct information. Your villagers will give you their pictures when you get it right.