Personalized I'm Nine Years Old with Dog and Mouse with White Text Hanes Youth Sweatshirts. 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 Nine Years Old with Dog and Mouse Black Youth Sweatshirt, perfect for young readers, helpers, and great friends on their birthday. Kids just want to keep warm and keep going. This sweatshirt does both and looks good too. 7.8 oz., 50/50 cotton/polyester. Double-needle stitched neckline and armholes. Rib waistband and cuffs.