Personalized Superhero 4th Birthday Toddler T-Shirt. This kid is Four! Celebrate your child's second b-day with this cute thumbs up 4th design. Happy Birthday 4-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.