Start by peeling your bananas and slicing them into rounds about ¼ inch thick, though you can adjust the thickness based on your preference. Set these banana slices aside while you prepare the creamy base.
In a medium mixing bowl, combine the whipped topping, sour cream, and dry pudding mix. Stir these ingredients together until they're fully combined and the mixture is smooth and creamy.
Gently fold in the marshmallows, mini Nilla wafers, and sliced bananas, being careful not to break up the banana pieces too much. Mix just until all ingredients are evenly distributed throughout the mixture.
You can serve this banana fluff immediately, but for the best results, cover and refrigerate for at least one hour to allow the cookies to soften and the flavors to meld together beautifully.
Notes
Banana Selection - Choose bananas that are ripe but still firm to prevent them from getting mushy when mixed into the salad.
Cookie Timing - If you prefer crunchier cookies, fold them in just before serving rather than letting them sit in the mixture.
Make-Ahead Success - This recipe actually improves with time, so don't hesitate to make it a day ahead for even better flavor development.
Serving Temperature - Serve this banana fluff chilled straight from the refrigerator for the best texture and most refreshing experience.