Personalized 4th Birthday Monster Toddler Long Sleeve T-Shirt. 4th birthday monster. A cute monster holds a bright yellow balloon to celebrate the four year old's fourth birthday! Great gift for your little 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.