Light coat a 12-cup muffin tin with cooking spray.
Combine the popcorn, pretzel pieces, 1 cup of the peanut butter chips and 1 cup of the milk chocolate chips in a large bowl. Toss to distribute evenly.
Melt the butter, confectioners’ sugar, corn syrup and marshmallows in a large microwave-safe bowl in 15 second intervals, stirring between each interval, until completely melted.
Pour the melted marshmallow mixture over the popcorn mixture and stir until evenly coated. Quickly, but gently form twelve 2 1/2-to-3-inch-diameter balls with either your hands or a large cookie scoop lightly coated with cooking spray. Pretend you’re making snowballs, but don’t pack them too hard. Place each of them in a well of the prepared muffin tin so they hold their shape as they cool.
When the popcorns balls are cool, melt the remaining 1/2 cup peanut butter chips, the remaining 1/2 cup milk chocolate chips and the white chocolate chips in each of 3 small microwave-safe bowls in 15 second intervals, stirring occasionally. Transfer the melted chips to each of 3 small piping bags or resealable bags. Snip the tips and drizzle over the popcorn balls. Top evenly with the crushed potato chips and let set, about 30 minutes, before serving.
Never leave a child unattended in the kitchen. Limit the child to tasks that are safe and age-appropriate.