Arrange gummy worms in ice cube trays, 1 worm per cube. Fill tray with fruit punch as you normally would water. Freeze until solid, 8 hours or overnight. Place into Witches Brew minutes before serving.
Pour the gelatin mix into a large bowl. Slowly stir in the boiling water. Stir at least 2 minutes, until the gelatin is completely dissolved. Stir in the pineapple juice. Let cool to room temperature.
Wearing heavy duty gloves or using tongs, place the block of dry ice in the bottom of the cauldron. (Dry ice will burn skin, so handle it with gloves and tongs and keep it away from kids and pets!)
Use an ice pick to break the block into smaller chunks, if necessary.
Fill the cauldron with just enough water to cover the dry ice. It will begin to steam.
Place the punch bowl inside the cauldron, on top of the dry ice. The cauldron will appear to be magically smoking.
Entrap the sterilized rubber hand between the cauldron and the punch bowl, squeezing it tight so the hand appears to be reaching out of the mist for help. Hot-glue the hand to the cauldron, if necessary, to hold it in place.
Carefully pour the drink mixture into the punch bowl. Slowly add the chilled vodka and lemon-lime soda or ginger ale. Stir gently to mix.