On a large baking sheet with a lip, spread the cereal in one layer. Also have a small bowl of sprinkles and counter space covered in wax paper prepped.
In a medium sauce pan or pot, melt 1/4 cup butter over medium heat. Use a heatproof rubber spatula or wooden spoon to gently swirl the butter all along the bottom and up the sides of the pan as it melts. Then add the marshmallows. Stir so all the marshmallows get coated in the butter as they begin to melt. Continue to stir occasionally until they have melted completely.
Pour over the cereal and gently toss so all the pieces get coated in the marshmallow mixture. Allow to cool for a minute or two.
Butter your clean hands and then gently press the cereal into balls about the size of a fist or a little smaller. Coat in sprinkles if using. Place on wax paper and continue forming balls until you've used up all the cereal.
