Personalized Hippo 1st Birthday Youth T-Shirt. Hippo 1st Birthday! I mean Happy 1st Birthday! A cute, smiling hippo wearing a birthday hat sits in front of a birthday cake ready to blow out the candle. Cute first birthday gift for the one year old! 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.