Combine caramel syrup and peanut butter in a small bowl. Fold in chocolate chips and chopped nuts.
Place popcorn in large bowl. Pour caramel over top; mix with hands (mixture will be sticky).
Using plastic wrap to prevent sticking, compress about 2 tablespoons popcorn mixture into 2-inch ball. Transfer to waxed paper. Continue with remaining mixture. Refrigerate if desired. Makes 2 dozen.