To a large mixing bowl add the instant pudding mix and milk then whisk for 5 minutes, or until the pudding is soft-set. Add the Cool Whip then fold with a spatula to combine and set aside.
To the bowl of an electric stand mixer fitted with the whisk attachment, or another large mixing bowl if using a hand-held mixer, add the softened cream cheese and butter then beat on medium-high speed until smooth and creamy, 30 seconds. Add the powdered sugar, mix on low until just combined, then turn the speed up and beat until the mixture is smooth and creamy, another 30 seconds. Scrape down the sides of the bowl.
Add the pudding mixture to the cream cheese mixture then mix on medium-high speed until everything is well combined. Use a spatula to give the mixture another couple of big stirs to ensure nothing has stuck to the bottom of the bowl then refrigerate until ready to use.
Add the Oreos
Spoon 1/3 of the pudding mixture (~heaping 2-1/2 cups) into the bottom of a 8.25
Cover the Dirt Cake then chill for at least 12 hours then top with gummy worms before scooping into bowls and serving. Leftover Dirt Cake will keep in the fridge for up to 5 days.