In large pot, melt butter on medium heat. Add in marshmallows and stir constantly until completely melted. Remove from heat. Fold in pudding mix until fully combined. Fold in cereal.
Immediately pour cereal into prepared baking dish. Using buttered fingers, press treats into dish (don't over press or they get hard and dry tasting).
Allow to set 20 minutes or more before cutting and eating. Enjoy!
Notes
Enjoy these delightful banana-flavored Rice Krispie treats!