It doesn't come as a great shock that the Mountain-Pygmy possum was once thought to be extinct. Tipping the scales at about 45 grams (a figure so small it's not even worth converting), the tiny marsupials scurry about at night in the remote alpine regions of Australia. In the spring and summer months, they stockpile food to be eaten during the winter, when they hibernate (first for a few days, then as the weather gets colder, for up to three weeks at a time). They were presumed extinct until found at a ski chalet in Australia in 1966, and the little guys are now listed under the Flora and Fauna Guarantee Act 1988.