For feet, place 2 gummy candies on cookie sheet. Spray inside of 1/4-cup measuring cup with cooking spray. For body, fill measuring cup with warm cereal mixture; place over feet, releasing cereal mixture and covering back half of feet. Repeat with remaining gummy candies and cereal mixture to make 24 aliens. Use 2 candy-coated chocolate candies for eyes and black decorating gel to make centers of eyes. Insert 2 pretzels for antennae.