Melt butter in a large saucepan over low heat and add marshmallows. Stir until they begin to melt, then remove from heat. Whisk in the (dry) cake mix, then stir in cereal so it is completely coated with marshmallow mixture. Sprinkle in half of the sprinkles and briefly stir. (Don’t stir too much or the sprinkles will bleed out their color.) Press the mixture into a baking dish (any size will do) and top with remaining sprinkles. Let sit for about 30 minutes before cutting. I find spraying a knife with nonstick spray helps to cut them cleanly.

*Disclaimer: You consume dry cake mix at your own risk.*