Personalized This Little Monster is One Toddler Long Sleeve T-Shirt. This Little Monster is One! A cute little green monster smiles because it is now one year old. Great birthday gift for your little 1 year old monster. 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.