Ahhh, Namo, while Nibbly is still smiling I think you need to find a Ziploc Bag. One of those heavyduty freezer types. Place the rodent in the bag, seal tightly getting out all that nasty air, then place in the freezer. Your little Mister will be there smiling every time you reach for an ice cube.
Rest in peace, Iflitifloat.