Personalized Pi Day Celebration Funny Math Toddler T-Shirt. Happy Pi Day math party school apple with Pi symbol on a Toddler T-Shirt - Vintage Smoke. 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.