While those onesies may have fit your child yesterday, babies seem to grow out of them faster than you can blink. Luckily, these little bodysuits transform into designer shirts for your favorite canine baby that are adorable and functional.
Choose the correct size onesie for your dog. Newborn onesies work for dogs less than 15 pounds. For larger dogs, choose the larger size. Place the onesie over your dog's head, with his front legs going through the armholes, to confirm the onesie fits correctly. Remove from your dog.
Cut a straight line on the bottom of the onesie to remove the button closures. Hem the edge of the shirt, and sew with needle and thread or sewing machine. This creates a doggie T-shirt.
Create a bodysuit for your dog instead of the T-shirt. Place the correct size onesie on your dog and mark the area on the onesie where your dog's tail is located using the fabric pen. Remove the onesie from your dog. Cut out a hole for your dog's tail. Fold the raw edge of the tail hole under and hem it with a needle and thread to finish the edge and keep it from unraveling. Place the onesie on your dog and attach the snap closures underneath.