Crush wafer cookies until crumbly. Add to a bowl with melted butter and salt. Stir to combine. Press into a 9 inch shallow pie pan firmly (no need to spray with nonstick as the butter provides double duty!).
Mix together pudding and milk, whisk to combine. In a separate bowl, mash 2 bananas with a fork. Fold bananas and Cool Whip into pudding.
Slice remaining 2 bananas and place evenly onto pie crust. Pour banana pudding mixture over bananas. Freeze for 6-8 hours before serving.
To serve, allow pie to thaw for 20 minutes at room temperature on kitchen counter. Top with extra Cool Whip and crushed cookies if desired.