Personalized Mermaid 1st Birthday Toddler T-Shirt. Mermaid 1st birthday! A cute little mermaid celebrates your first birthday with her fish friends. Cute gift for the one year old. A toddler-soft cotton tee in look-at-me, big kid colors. 4.5 oz., 100% combed ringspun cotton. White is sewn with 100% cotton thread. Topstitched rib crew neck. Double-needle stitched sleeves and bottom hem. Shoulder-to-shoulder taping.