Put the cookies in a food processor and pulse until finely ground. Add the butter and process until crumbly. Press the crumb mixture evenly onto the bottom and up the sides of a 9-inch pie plate.
Soften the gelatin in 1/4 cup water for 5 minutes and set aside. Combine the marshmallow creme, candies and milk in a small saucepan over low heat and cook, stirring occasionally, until the candy melts, 5 to 6 minutes. Transfer the marshmallow mixture to a large bowl. Stir in the gelatin mixture until blended. Let cool to room temperature; fold in the whipped topping. Pour the mixture into the crust. Chill until set, at least 4 to 6 hours.