Flannel is a common material for making Christmas onesies, since it’s soft, warm, and breathable. It’s also a great choice for people who suffer from allergies, because it won’t irritate the skin. <br> <br>Another popular option for Christmas onesies is footies, which are integrated into the design. This adds an extra layer of warmth and comfort to a onesie, though you might not always want them on. They can also be impractical, since they don’t always fit in your shoes and aren’t removable.