From the Dr. Seuss Clothing Collection. Dr. Seuss Hatter And Co. Toddler Sleep Set. This two piece boy's sleep set features the Cat in the Hat on the front of the red t-shirt and reads "The Cat in the Hat by Dr. Seuss" in white, distressed print. The bottoms are gray with white and red jersey stripes down the side and features a Cat in the Hat's hat emblem. Made of 100% polyester jersey.