Personalized Cute 6th Birthday Penguin Youth T-Shirt. 6th Birthday Party Penguin Youth T-Shirt - Vintage Royal Blue gift idea for your child's 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.