Personalized Monster 1st Birthday Youth T-Shirt. Cute 1st birthday Youth T-Shirt - White with a funny cartoon purple monster, stars and polka dotted number 1 says THIS LIL' MONSTER IS ONE! 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.