Preheat and Prep: Preheat the oven to 325°F (163°C). Lightly grease a 9-inch springform pan.
Make the Crust: Combine the crushed vanilla wafer cookies, granulated sugar, and melted butter in a bowl. Press the mixture firmly into the bottom of the springform pan, covering the base evenly. Bake for 10 minutes and let it cool.
Prepare the Cheesecake Filling: Beat the softened cream cheese and granulated sugar together in a large bowl until smooth. Add sour cream and vanilla extract, mixing well. Beat in the eggs one at a time, followed by the mashed bananas.
Assemble and Bake: Pour the cheesecake filling over the cooled crust. Place the springform pan on a baking sheet and bake for 55-65 minutes, or until the center is slightly jiggly. Let it cool in the oven with the door ajar for 1 hour, then refrigerate for at least 4 hours or overnight.
Make the Banana Pudding Layer: Whisk the banana pudding mix with cold milk until thickened. Spread it evenly over the chilled cheesecake.
Prepare the Whipped Topping: Beat the heavy whipping cream and powdered sugar together until stiff peaks form. Spread or pipe the whipped cream over the banana pudding layer.
Garnish and Serve: Top with sliced bananas and vanilla wafer cookies for decoration. Slice and enjoy!