Personalized Dyngus Day Babys 1st Polish T-Shirt. My 1st Dyngus Day T-Shirt - White with colorful rooster design for celebrating this fun Polish American day after Easter holiday. 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.