In Hongdae: Daiso Hongdae Store 2 (182 Yanghwa-ro) and Hongik Univ. Entrance Store (25 Hongik-ro), 10am–10pm. Store 2 is right around Hongik Univ. Station, a short walk from the exit. Hologram Alien Glasses (silver) are ₩1,000 and make funny photos. The props are light enough to drop in your bag after. Hongdae is packed on weekends, so weekday evenings are easier.
