In a medium-sized bowl, whisk together milk and instant banana pudding mix for about 2 minutes, or until the pudding mix has thickened slightly.
Let the pudding mixture sit in the refrigerator for about 15-30 minutes to thicken further.
Gently fold in 1 cup of whipped cream or whipped topping into the pudding mixture until well combined. Set aside the remaining whipped cream or topping for later use.
Take a mini-Nilla wafer bag and carefully fill it with a layer of the banana pudding mixture, using a spoon.
Add a layer of sliced bananas on top of the pudding.
Repeat layering the pudding mixture and sliced bananas until you reach the desired amount, leaving some space at the top.
Once you've filled the bags, place the Nilla wafer bags in the refrigerator and let them chill for at least 1 hour, or until the pudding is set and the flavors have melded together.
When ready to serve, remove the chilled Nilla wafer bags from the refrigerator. Add a dollop of cool whip and sprinkle crushed vanilla wafer on top, don’t forget to top with a sliced banana. Serve the walking banana pudding bags immediately and enjoy!