World's Greatest Dad or Grandpa Sweatshirt He is one in a million and he is all yours. Let him know he is the greatest with our Personalized "World's Greatest" Sweatshirt. Available on our premium white cotton/poly blend Personalized Sweatshirt, machine washable in adult sizes S-3XL. Also available in Ash Gray. Includes FREE Personalization! Personalize your Sweatshirt with any title and up to 30 names.