Start by crushing the Oreo cookies into fine crumbs. You can do this by placing them in a plastic bag and using a rolling pin or a food processor.
In a large mixing bowl, combine the softened cream cheese and powdered sugar. Use an electric mixer or whisk until fully blended and smooth.
Gently fold in the thawed Cool Whip until there are no lumps. This will create a fluffy cream cheese mixture.
In another bowl, whisk together the instant chocolate pudding mix and milk. Mix until it thickens, approximately 2 minutes.
In the 9x13 inch baking dish or trifle dish, layer half of the crushed Oreo cookies on the bottom.
Spread half of the cream cheese mixture over the cookie layer, followed by half of the chocolate pudding mixture.
Repeat the layers with the remaining crushed cookies, cream cheese mixture, and chocolate pudding mixture.
Finish the top layer with the remaining crushed Oreo cookies, creating a 'dirt' appearance.
Decorate the top with gummy worms and Cadbury mini eggs for a festive look.
Refrigerate the cake for at least 1 hour before serving to let the flavors meld.