Serve root-beer floats from a "steaming" cauldron made magical with the smoke of dry ice.
You'll need a large cauldron and a chilled bowl that fits inside it (dry ice can cause glass to crack, so use bowls made of metal); dry ice (available in supermarkets); frozen root-beer mugs; root beer; and ice cream. Wearing gloves, use an ice pick to break up the dry ice (never touch it with your bare hands); place a few pieces in the cauldron. Cover the ice with water, pushing the ice under with a long wooden spoon if necessary, and place the chilled bowl in the cauldron. Fill the bowl with root beer. Put a scoop of ice cream in each mug, and ladle root beer over the top.