Preheat oven to 325°F (160°C).
In a medium bowl, combine graham cracker crumbs, melted butter, and sugar; mix until evenly coated.
Press crumb mixture firmly into the bottom of a 9-inch springform pan and bake for 10 minutes; let cool.
In a large bowl, beat softened cream cheese and sugar until smooth and creamy.
Add vanilla extract and eggs one at a time, mixing well after each addition.
Mix in sour cream and mashed banana until combined.
Pour cheesecake filling over the cooled crust and spread evenly.
Bake for 50-60 minutes until edges are firm but center is slightly jiggly.
Turn off oven and leave cheesecake inside with the door slightly open for 1 hour to cool.
Remove cheesecake and chill in the refrigerator for at least 4 hours or overnight.
In a large bowl, whisk banana pudding mix with whole milk until thickened.
Pour the banana pudding layer over chilled cheesecake and spread smooth.
Refrigerate cheesecake with pudding layer for an additional hour.
Before serving, top with sliced bananas, crushed graham crackers or vanilla wafers, and optional whipped cream.
Slice, serve chilled, and enjoy your Banana Pudding Cheesecake.