The event plaza on Teacher's Day.
Teacher's Day is an event in Animal Crossing: New Leaf that occurs on May 15. It appears only in Korean towns. During the event, Isabelle appears in the Event Plaza and will give the player a Red-Carnation Bag if spoken to. If Teacher's Day coincides with a Fishing Tourney, Isabelle instead appears outside Town Hall, as Chip occupies the plaza; however, the standee still appears in the plaza.
Teacher's Day coincides with the holiday of the same name, observed in several countries. In South Korea, where it is observed on May 15, students generally present their teachers with carnations, an element referenced in the game with Isabelle's gift.