In a large bowl stir together 2 1/2 cups Oreos and butter until well combined.
Press mixture evenly and firmly into the bottom of springform pan.
Freeze crust for at least 20 minutes.
In a large bowl combine cream cheese, powdered sugar, cake mix, vanilla extract, and milk (if needed).
Fold in Cool Whip & vanilla extract.
Fold in crushed oreos and rainbow sprinkles.
Give it a taste, add more sugar if desired.
Pour into prepared pan and spread into an even layer.
Freeze for 2-3 hours or refrigerate overnight, or until set.
Decorate as desired.
If completely frozen, allow to sit at room temperature to soften up a bit before cutting.