Personalized Leprechaun Happy St Patricks Day Irish T-Shirt. Happy St Patrick's Day Leprechaun T-Shirt - Navy Blue has Irish greeting for baby's 1st St Paddys Day celebration. 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.