Personalized Unicorn 6th Birthday Youth T-Shirt. Unicorn 6th Birthday - A pastel unicorn jumps over a colorful rainbow and smiling cloud. Cute gift for the six year old's sixth birthday! 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.