Fireman One-piece Costume Baby Onesies. Our collection of baby and infant onesies will make your baby a funny baby! Our Fireman One-piece Costume Baby Onesies Baby have been hand picked by GoneBlue's humorists so you know they are going to be hysterical. Will these onesies make your friends and family laugh? We think so! Not matter what your baby is sure to look cute as a button in these onesies. Each onesies is made of 100% cotton and feature a perfect fit collar that automatically adjusts to your baby so baby will love them too! These onesies are sure to be soft and comfy.