Preheat the oven to 350 degrees. Coat the 9x13 baking pan with cooking spray or grease and flour pan, tapping out the excess flour. Set aside.

Using an electric stand mixer fitted with a paddle attachment, beat the cake mix, pudding mix, water, oil and eggs on medium speed for 2-3 minutes or until well blended. Scrape the sides of the bowl and mix again until all the ingredients are incorporated.

Pour the batter into prepared cake pan. Place the pan in the preheated oven and bake for 35-40 minutes or until a toothpick inserted into the center comes out clean.

Remove the pan from the oven and place on a wire cooling rack for 25-30 minutes. Let cool completely before making the cake pops.

Mash up the cake and place in a large bowl. Using an electric stand mixer fitted with a paddle attachment, mix the cake, oreos and 1/2 to 3/4 cup buttercream frosting on medium sped until well blended and the mixture can be formed into a ball.

Measure and roll mixture into 1 tablespoon-size balls and place on a cookie sheet. Refrigerate for 30-60 minutes or until firm.

Melt the candy melts in a microwave-safe bowl in 30 second increments for about 2 1/2 minutes at 40% power, stirring as needed until smooth. Remove the bowl from the microwave.

Remove the pops from the refrigerator. Dip each lollipop stick 1/4 inch into the melted candy. Insert the sticks into all the cake balls. (The melted candy will adhere the lollipop sticks to the cake balls to prevent them from falling off the sticks when dipping). Proceed to dip entire cake balls down into melted candy. Use a spool to sprinkle rainbow jimmies over the cake pops until completely covered.

Stand the pops in a sheet of styrofoam to dry.