Personalized I'm One Superhero Toddler Long Sleeve T-Shirt. I'm One! Superhero toddler in a red cape and diaper is ready to fight crime and nap time. Cute gift for any superhero one year old's 1st 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.