Personalized I'm Six Years Old with Dog and Mouse Long Sleeve T-Shirt. Celebrate your birthday with Dog and Mouse, the unlikely best friends from the children's book "Dog and Mouse" by Michelle Nelson-Schmidt. I'm Six Years Old with Dog and Mouse Long Sleeve T-Shirt - Purple, perfect for young readers, helpers, and great friends on their birthday. Pre-shrunk 100% cotton 6.1 ounce long sleeve t-shirt. Double-needle stitched neckline and sleeves. Quarter turned. Shoulder-to-shoulder taping. Adult: S, M, L, XL, 2XL, 3XL