Preheat oven to 350°F (175°C). Combine crushed vanilla wafers, pecans, and melted butter. Press the mixture into the bottom of a springform pan. Bake for 10 minutes, then let cool completely.

In a large bowl, beat cream cheese and sugar with an electric mixer until smooth and creamy. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract, optional mashed banana, and optional lemon juice.

Pour the filling into the prepared crust. Place the springform pan in a water bath (larger baking pan filled with hot water). Bake at 325°F (165°C) for 60-70 minutes, or until the edges are set but the center still jiggles slightly.

Turn off the oven and let the cheesecake cool in the water bath for 30 minutes. Remove from the water bath and let it cool completely at room temperature. Cover and refrigerate for at least 4 hours or overnight.

Before serving, top with whipped cream, sliced bananas, and crushed vanilla wafers.