In a 4-quart freezer container, combine the pineapple juice, orange juice, rum (if desired), lemonade concentrate, oranges, and cherries.
Cover and freeze overnight or until frozen through. To form slush, scrape a large spoon across the frozen mixture; spoon into a punch bowl. Slowly pour ginger ale down the side of the punch bowl; stir.
Serve in tall glasses. If desired, garnish each drink with strips of pineapple for creepy fingers, honeydew melon balls studded with blueberries for eyeballs, and a mandarin orange for a nose.