Personalized Dinosaur 3rd Birthday Toddler Long Sleeve T-Shirt. A dinosaur apatosaurus (or brontosaurus to the grandparents) stands tall over the 3 for the second birthday. Happy third birthday to the three year old! A classic for Fall, Winter and Spring, these long sleeve toddler t-shirts are sure to be a staple in your child's wardrobe. Whether layered or alone, this t-shirt is soft yet durable enough to stand up to your toddler's playtime demands.