Personalized So Cute Birthday T-Shirt. Cute birthday T-Shirt - Green with colorful sprinkles and I'M SO CUTE IT MUST BE MY BIRTHDAY saying. For the birthday boy or girl. Everyone loves our Custom T-Shirts! Wardrobe essential for looking good, 24/7. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar. Shoulder-to-shoulder taping. Double-needle stitched sleeves, bottom hem and front neck. Note: greys are a cotton/polyester blend.