Personalized 4th Birthday Cute Penguin Youth T-Shirt. 4th Birthday Youth T-Shirt - Black has cute penguin in a party hat with the number 4 on its tummy for your child's fourth birthday celebration. Let the good times roll in a durable T-Shirt that takes kids from school to play in an amazing array of colors. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar.