Personalized I'm One Dinosaur Toddler Long Sleeve T-Shirt. I'm One! A grinning dinosaur wearing a birthday hat rips through the shirt to wish the little one year old a happy birthday! 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.