Preheat oven to 350 degrees. Grease and flour a 9x13 cake pan.
In a mixing bowl, add cake mix, eggs, 1 cup of milk, and melted butter and beat on low until well incorporated, scraping bowl often.
Pour cake batter into prepared pan, then bake in preheated oven for 27-28 minutes or until cake is baked through.
Remove cake from oven and allow to cool completely.
Using the end of a wooden spoon, poke holes into the top of the cake.
Prepare instant pudding by whisking with remaining cold milk, then pour slowly over the top of the cooled cake. Pudding mixture should sink down into the holes in the cake. Then refrigerate for a minimum of an hour.
Add whipped topping to a mixing bowl, then gently fold in unsweetened cocoa. Then spread over top of cake.
Top with cereal, then serve and enjoy! If planning on serving later, wait to top with cereal.