Heat oven to 350°F. Line 24 muffin cups with paper baking cups. Prepare and bake cupcakes as directed on cake mix package, using water, oil and egg whites. Cool 20 minutes or until completely cooled.
With apple corer or small knife, make 3/4-inch hole from top center to bottom of cupcake. (Do not pierce paper baking cups.)
Place frosting in resealable food storage plastic bag; seal bag. Cut 1/2-inch hole in bottom corner of bag. Pipe frosting into each hole. Place gummy worm on top of each cupcake.