HEAT oven to 350°F.
PREPARE brownie batter as directed on package. Spread onto bottom of 12-inch pizza pan sprayed with cooking spray. Bake 18 to 20 min. or until toothpick inserted in center comes out with fudgy crumbs. (Do not overbake.) Cool completely.
DISSOLVE 4 Tbsp. (1/4 cup) drink mix in hot water in large bowl. Add cream cheese and butter; beat with mixer until blended. Gradually add sugar, beating until blended. Spread evenly over brownie.
SPRINKLE remaining drink mix onto frosted brownie in 5 curved lines to resemble a pumpkin. Place fruit snack roll on center top of pumpkin for "stem." Create "eyes" and "mouth" using decorating icing. Place cookies on eyes for "pupils." Add candy corn in mouth for "teeth."