From the Dr. Seuss Clothing Collection. Dr. Seuss Thing 1 and Thing 2 Racers Toddler Sleep Set. This two piece boy's sleep set features Thing 1 and Thing 2 racing together across the front of the blue t-shirt and reads "by Dr. Seuss." The bottom is navy with white and blue jersey stripes down the side and features the Cat in the Hat emblem. Made of 100% polyester jersey.