Add boiling water to gelatin mix in medium bowl; stir 3 min. until completely dissolved. (Do not add cold water.)
Pour into 15x10x1-inch pan sprayed with cooking spray. Refrigerate 3 hours or until firm. Meanwhile, prepare cake batter and bake as directed on package for 24 cupcakes. Cool completely on wire racks.
Dip bottom of 15x10x1-inch pan in water 15 sec. Use 2-inch round cookie cutter to cut 24 JIGGLERS from gelatin.
Cut cupcakes horizontally in half.
Place 2 tsp. COOL WHIP on bottom half of each cupcake; top with 1 JIGGLERS and 2 tsp. COOL WHIP. Cover with tops of cupcakes; press gently into COOL WHIP to secure. Top with remaining COOL WHIP and sprinkles.