Heat oven to 350°F (325°F for dark or nonstick pan). Line 8-inch or 9-inch square pan with foil so foil extends about 2 inches over sides of pan. Spray foil with cooking spray. Make brownies as directed on box. Cool completely, about 1 hour.
Place brownies in freezer for 30 minutes. Remove brownies from pan by lifting foil; peel foil from sides of brownies. Cut brownies into 15 rectangular bars, 5 rows by 3 rows. Gently insert craft stick into end of each bar, peeling foil from bars. Place on cookie sheet; freeze 30 minutes.
In small microwavable bowl, microwave chocolate chips and shortening uncovered on High about 1 minute; stir until smooth. If necessary, microwave additional 5 seconds at a time. Dip top 1/3 to 1/2 of each brownie into chocolate; sprinkle with candy sprinkles. Lay flat on waxed paper or foil to dry.