Preheat the oven to 350 degrees, and grease a 13 x 9-inch cake pan.
In a large bowl, mix pudding and milk. Add cake mix and 1 cup crushed cookies and stir to combine. Transfer to the cake pan and smooth into an even layer. Bake for 30 minutes. Cool completely, about 1 hour.
In a large chilled bowl, beat cream until stiff peaks form. Fold in 1 cup of the remaining crushed Oreos. Cover cake with whipped cream. Add more crushed Oreos and rainbow sprinkles. Scoop to serve.