What mechanisms or metabolisms do animals use to survive outdoors when the temperature is 10° below zero?

Seriously.

I often look at sparrows and wonder how they can survive a normal winter, much less 2–5 days of below zero temperatures.

How do tree frogs weather winter?

Insects, even. If water is the basis on life on Earth, how do the eggs not burst or shrivel?

This is a “Fun Facts” where you can share knowledge of a critter you know a lot about, for whatever reason.