Personalized Superhero 4th Birthday Pink Toddler Long Sleeve T-Shirt. Happy 4th birthday! Celebrate your toddler's third b-day with this cute I'm 4 pink superhero design. Happy Birthday four-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.