Grease a 9 x 13-inch baking dish with cooking spray to prevent sticky treats.

Crush the Circus Animal Cookies using a food processor and reserve ½ cup for topping.

Melt unsalted butter and mini marshmallows in a large pot over low heat, stirring until fully melted.

Combine Rice Krispies, crumbled cookies, 1 tablespoon of nonpareils, and 1 tablespoon of colored sprinkles with the melted mixture.

Spread the mixture evenly in the prepared dish and press down gently to compact.

Sprinkle the reserved cookie pieces over the top of the pressed mixture.

Melt the white chocolate chips in a microwave-safe bowl by microwaving in 30-second intervals until smooth.

Drizzle the melted white chocolate over the treats using a zip bag as a drizzling tool.

Allow treats to cool at room temperature until set, around 30 minutes.