Personalized Superhero 1st Birthday Baby Sweatshirt. Happy 1st birthday! Celebrate your baby's first b-day with this cute I'm 1 superhero design. Happy Birthday one-year-old! Keep your little one warm and comfortable with this soft infant crew fleece sweatshirt. Made from a cozy cotton poly blend, this pullover offers just the right amount of warmth for cooler days without feeling bulky. The snap-tape neck closure makes dressing quick and easy, and the ribbed collar, cuffs, and hem provide a secure fit that moves with your baby. Durable stitching and side-seam construction help the sweatshirt maintain its shape and softness through repeated washing. Great for everyday wear, daycare, playtime, or layering during fall and winter, this fleece sweatshirt is a practical and comfortable essential for any baby wardrobe.