Personalized 3rd Birthday Mermaid 3 Year Old Girl Adult Sweatshirt. Cute mermaid themed 3rd birthday outfit for a toddler girl with number 3 design. Stay warm and stylish with this classic adult sweatshirt, perfect for everyday comfort. Crafted from soft, durable fabric, it features a relaxed fit for added coziness. Whether you’re lounging at home, running errands, or enjoying outdoor activities, this versatile sweatshirt is a wardrobe essential for any season.