Gather all your ingredients and supplies—a large pot, spatula, mixing bowl, and a 9x13 inch baking dish. Grease the baking dish lightly for easy removal later.

In a large pot over low heat, melt the unsalted butter, stirring occasionally to avoid burning.

Once the butter is melted, add in the mini marshmallows and stir until completely melted and smooth. You can add vanilla extract at this stage.

Quickly add the rice cereal to the melted marshmallow mixture, folding it together gently with the spatula until all the cereal is evenly coated.

Transfer the mixture to the greased baking dish and press down firmly into an even layer.

While the mixture is still warm, sprinkle colorful toppings across the surface. Allow it to cool completely for about 30 minutes to set.

Once cool, cut the treats into squares and serve.