That's right, make your own personalized adult-sized onesie. Onesies are popular pajamas for lounging at home, getting discounts on brunch on weekends, or even participating in a onesie run. A one piece sweatsuit is a modern adult's wardrobe staple.These custom adult onesies have a unisex fit and are incredible loungewear. Create your own personalized adult onesie with photos of pets and more. Sold and shipped by Etsy.