Step 1: Prepare the 'dirt' by crushing the Oreo cookies. Place them in a food processor and pulse until fine crumbs are formed, or put them in a large resealable bag and crush with a rolling pin.
Step 2: In a large bowl, whisk together the instant chocolate pudding mix and cold milk for 2 minutes, or until the mixture begins to thicken. If using, gently fold in the thawed whipped topping for an extra creamy texture.
Step 3: Begin assembling the dirt cups. Place a layer of crushed Oreos (about 1-2 tablespoons) at the bottom of 6-8 individual clear cups or small dessert glasses.
Step 4: Spoon a layer of chocolate pudding mixture over the Oreo crumbs, filling about one-third of the cup.
Step 5: Add another layer of crushed Oreos, followed by another layer of pudding. Repeat until the cups are nearly full, ending with a generous top layer of crushed Oreos to resemble 'dirt'.
Step 6: Place the assembled dirt cups in the refrigerator to chill for at least 2 hours, allowing the pudding to fully set.
Step 7: Just before serving, decorate your graveyard. Insert one rectangular cookie into the 'dirt' at the edge of each cup to serve as a 'tombstone.' Arrange 1-2 gummy worms so they appear to be crawling out of the 'dirt.' Add any additional Halloween candies for a more festive look.