Preheat your oven to 350°F (177°C) and prepare a 9" X 13" baking pan with nonstick spray.

In a large mixing bowl, follow the brownie mix instructions and whisk the required ingredients. Pour half the batter into the prepared pan.

In a separate bowl, mix creamy peanut butter, unsalted butter, light brown sugar, granulated sugar, eggs, and vanilla extract until fluffy.

In another bowl, combine flour, baking soda, kosher salt, oats, and chocolate chips. Fold into the peanut butter mixture until just combined.

Drop dollops of the mixture onto the brownie layer in the pan, sprinkle with Halloween sprinkles and add candy eyes on top.

Bake in the preheated oven for 25 to 30 minutes, until a toothpick comes out clean or with a few moist crumbs.

Cool the brownies in the pan for at least 30 minutes before lifting them out using parchment paper.

Beat together butter, confectioners sugar, heavy cream, and gel food coloring until smooth for the frosting.

Once cooled, frost each brownie and arrange candy eyes. Allow frosting to set before cutting and serving.