In a saucepan over medium heat, combine the corn syrup, margarine, cold water, confectioners' sugar and marshmallows. Heat and stir until the mixture comes to a boil, add vanilla. Carefully combine the hot mixture with the popcorn, coating each kernel.
Grease hands with vegetable shortening and quickly shape the coated popcorn into balls before it cools. Wrap with cellophane or plastic wrap and store at room temperature.