Begin by preparing the chocolate and vanilla pudding according to the package directions, using 2 cups of cold milk for each. Whisk thoroughly until smooth and set aside to thicken for about 5 minutes.

While the puddings set, crush the Oreos into fine crumbs using a food processor or by rolling over a zip-top bag with a rolling pin. Melt the unsalted butter, then combine it with the crushed Oreos. Press this mixture firmly into the bottom of a casserole dish to form a solid crust.

In a mixing bowl, add softened cream cheese and powdered sugar. Beat with an electric mixer on medium speed until smooth and creamy, about 2 minutes. Gently fold in whipped topping until fully integrated.

Spread the cream cheese mixture evenly over the Oreo crust, then pour the vanilla pudding layer over the cream cheese, followed by the chocolate pudding on top.

Cover the assembled casserole with plastic wrap and refrigerate for a minimum of 3 hours, or overnight if time allows.

Just before serving, remove from the refrigerator, take off the plastic wrap, and top with crushed Oreos and Easter-themed candies.