Combine softened cream cheese and sugar in mixing bowl. Beat with an electric mixer on low speed until creamy. Add sour cream and vanilla, beat until well combined. Stir in cool whip and crushed cookies. Spoon mixture into pie crust using a rubber spatula to spread evenly. Refrigerate for 4 to 5 hours before serving.
To decorate: Through a fine sifter, heavily sprinkle cocoa powder over the cake to make it look like dirt in a graveyard.
To make tombstone cookies scrape the cream filling out of chocolate cookies. Cut off ends of cookies so as to make a rectangular shape.
Using royal icing in a piping bag, pipe spooky decorations and words on the tombstone cookies. Examples: BOO, RIP.