Personalized I'm Three Mendous Toddler Long Sleeve T-Shirt. I'm Three Mendous! Pow! Wow! Third birthday comic book style for your tremendous little superhero. Great 3rd birthday present. 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.