Personalized 6th Birthday Superhero Toddler Long Sleeve T-Shirt. Pow! Happy birthday to the 6 year old! 6th birthday gift for your little superhero. 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.