Combine vanilla pudding, sour cream, and milk in a bowl; beat at low speed with an electric mixer for 2 minutes or until thickened. Add in one half of whipped topping. Line bottom and sides of a 3 quart bowl (or casserole dish) with vanilla wafers. Slice one banana and layer over wafers.. Spoon 1/3 of pudding mixture over bananas. Repeat layers of vanilla wafers, bananas and pudding twice. Top with remainder of whipped topping. Chill. Servers 10-12. Best if made night before to allow pudding to set up and flavors to work together.