Personalized This will be the Best Birthday Ever T-Shirt. While all birthdays are worth celebrating, this one will be the best ever! This will be the Best Birthday Ever T-Shirt - Athletic Heather, featuring Mouse from the children's book "Dog and Mouse" my Michelle Nelson-Schmidt. 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.