Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan.
In a large mixing bowl, melt the butter and stir in the sugar until well combined.
Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.
In a separate bowl, sift together the flour, cocoa powder, and salt.
Gradually add the dry ingredients to the wet mixture, stirring until just combined.
Fold in the mini marshmallows and crispy rice cereal until evenly distributed.
Pour the brownie batter into the prepared baking pan and spread it evenly.
Sprinkle the top with red and blue sprinkles.
Bake for 25-30 minutes or until a toothpick inserted in the center comes out with a few moist crumbs.
Allow the brownies to cool in the pan for at least 15 minutes before cutting into squares.
