When the temperature really dips—like to the point where Californians would wail, drop their Double-Doubles and die—it’s necessary to maximize your coziness. If the thermometer has frozen, it's time to break out the "Union Suit," which you may know by it's other name: the onesie. The one-piece, butt-flapped undergarment of yesteryear has evolved into several very comfortable modern options, including onesies with footies and the exotic slanket. Though you'd never venture out in public with any of these things on, you definitely want to have them at home. Here are eight we love and one we find kind of terrifying.