Personalized Birthdaysaurus Rex Youth T-Shirt. Birthdaysaurus Rex - A cute, smiling T-Rex dinosaur wearing a birthday party hat and holding a cupcake. Great gift for any dino lover! 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.