Once Upon a Child Harrisburg is a popular destination for parents looking to buy and sell quality children's items at great prices. Customers praise the store's cleanliness, organization, and friendly staff who are always willing to assist. The process of selling used clothes is straightforward, and sellers are generally satisfied with the payouts they receive, though one reviewer noted an unsatisfactory experience where items were not thoroughly examined. Overall, the store is described as a "whole gem" for parents, offering a convenient and cost-effective way to refresh their children's wardrobes. Customers recommend the store and appreciate the opportunity to find high-quality items without breaking the bank.