Microwave popcorn as directed on bag.
Meanwhile, in 3-quart saucepan, melt marshmallows, butter and peanut butter over low heat, stirring constantly, until smooth. Remove from heat; cool slightly.
In large bowl or roasting pan, mix popcorn, peanut butter pieces and candies. Pour marshmallow mixture over popcorn mixture; stir until well coated. Cool slightly.
Spray hands with cooking spray. Shape popcorn mixture into balls, each about 3 inches in diameter. Place on waxed paper; cool. Wrap individually in plastic wrap, or place in plastic bags and tie with ribbon or raffia.