Personalized I'm One Years Old with Dog and Mouse Toddler 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 One Year Old with Dog and Mouse Toddler T-Shirt - Heather and Hot Pink, perfect for young readers, helpers, and great friends on their birthday. A toddler-soft cotton tee in look-at-me, big kid colors. 4.5 oz., 100% combed ringspun cotton. White is sewn with 100% cotton thread. Topstitched rib crew neck. Double-needle stitched sleeves and bottom hem. Shoulder-to-shoulder taping.