In celebration of Grandparents Day on Sunday, 9/9, get 4 Original Sliders for $1 at White Castle with any purchase by a grandparent for a grandchild when you present the coupon found here. Plus, be one of the first 100 people to celebrate Grandparents Day with your family at White Castle and get a FREE vintage paper cap. *$1 Sliders not valid with online orders or other coupons or discounts. Limit 1 per customer per visit. Cheese and Bacon are extra.