Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper or silicone mats.

In a large mixing bowl, cream the room temperature unsalted butter, granulated sugar, and light brown sugar using an electric mixer on medium speed for about 2 minutes.

Add the eggs one at a time, mixing thoroughly after each addition, then pour in the vanilla extract.

In a separate medium bowl, whisk together the flour, baking soda, and salt, then gradually add to the wet ingredients, blending gently.

Fold in the Fruity Pebbles cereal and white chocolate chips gently, adding rainbow sprinkles if desired.

Using a cookie scoop, drop 1.5-inch portions of dough onto the prepared baking sheets, leaving about 2 inches between each scoop.

Bake for 10-12 minutes until the edges are golden brown and centers appear slightly undercooked.

Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.