In a large mixing bowl, melt the butter in the microwave, then add the marshmallows and stir until fully melted.

Add glow-in-the-dark glitter to the melted mixture and stir until evenly combined.

Fold the Rice Krispies cereal into the marshmallow mixture until well coated.

Press the mixture into a greased 9x13 inch baking pan, smoothing the top with a spatula.

Let the treats cool for about 30 minutes before cutting them into squares.