Personalized 12th Birthday Party Youth T-Shirt. 12th Birthday Youth T-Shirt - White has colorful polka dot number 12 and Time To Party quote on this great bday celebration gift. 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.