In a saucepan over medium heat, combine butter, brown sugar, and mini marshmallows. Stir constantly until mixture is completely melted and smooth.

Place the popcorn in a large bowl, and then pour the hot mixture over the top of the popcorn. Add in the marshmallow cereal and liberally dust with green sprinkles. Use a large spatula to mix ingredients and combine everything well.

Grease two clean, plastic kitchen gloves with cooking spray and begin to shape the coated popcorn into balls (about tennis ball size). Set inside of a muffin tin to finish cooling. Store in an airtight container when finished.