For the Cupcakes:
Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners.
In a large bowl, combine the cake mix, mashed bananas, buttermilk, vegetable oil, eggs, and vanilla extract. Use an electric mixer on medium speed to blend the ingredients until smooth.
Divide the batter evenly among the cupcake liners, filling each about 2/3 full.
Bake for 18-20 minutes or until a toothpick inserted into the center of a cupcake comes out clean.
Remove the cupcakes from the oven and allow them to cool completely on a wire rack.

1. For the Pudding Filling:
   In a medium bowl, whisk together the instant vanilla pudding mix and cold milk.
   Stir in the vanilla extract. Continue whisking for about 2 minutes, or until the pudding begins to thicken.
   Cover the pudding and place it in the refrigerator to set for about 10 minutes.
2. For the Topping:
   In a large mixing bowl, whip the heavy cream with an electric mixer until soft peaks form.
   Add powdered sugar and vanilla extract, and continue whipping until stiff peaks form.
3. Assembling the Cupcakes:
   Once the cupcakes are completely cooled, use a small knife or cupcake corer to create a hole in the center of each cupcake.
   Spoon the vanilla pudding into the center of each cupcake, filling the hole with a generous amount of pudding.
   Pipe or spoon the whipped cream on top of the cupcakes, creating a swirl or mound of whipped topping.
   Garnish each cupcake with a mini vanilla wafer on top for that authentic banana pudding look.