Fill ice cube trays with water, and place a candy gummy worm into each cube. Freeze the ice cubes solid, 1 to 2 hours.
Arrange the location for the cauldron, and place the glass bowl inside. Wash the plastic eyeballs, and set aside.
Pour lemon-lime soda, seltzer water, rum, and pineapple-orange-banana juice into glass bowl inside cauldron, and stir gently to mix. Mix in the plastic eyeballs, gummy worm ice cubes, and frozen melon balls. With tongs, gently add pieces of dry ice for smoke effect. Be careful; dry ice is so cold it will burn if it is ingested or touches skin. Serve in punch cups. Make sure whoever serves brew does not get dry ice in drinks!