Personalized Happy Pi Day Math Lover Party Toddler Long Sleeve T-Shirt. Pi Day math themed Toddler Long Sleeve Tee - Black has pi symbols in a pie. Fun gift for a geek, math teacher, college math major or any math lover. 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.