Personalized 5th Birthday Mermaid Party Youth T-Shirt. Cute 5th birthday mermaid Youth T-Shirt - Vintage Hot Pink with a blue mermaid tail for a 5 year old party. 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.