Personalized Monster 3rd Birthday Youth T-Shirt. Cute 3rd birthday Youth T-Shirt - White with a funny cartoon purple monster, stars and polka dotted number 3 says THIS LIL' MONSTER IS THREE! 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.