Melt the butter in a large saucepan over low heat.
Add the mini marshmallows and stir until completely melted and smooth.
Remove from heat and stir in the vanilla extract.
Add the Rice Krispies cereal to the marshmallow mixture and stir until well coated.
Gently fold in the sliced bananas, being careful not to mash them.
Press the mixture evenly into a greased 9x13 inch baking dish.
Allow it to cool for about 30 minutes at room temperature.
Once cooled, spread the whipped topping over the top of the Rice Krispie treats.
Sprinkle the crushed vanilla wafers and ground cinnamon evenly over the whipped topping.
Cut into squares and serve. Enjoy your delicious Banana Pudding Rice Krispie Treats!