Hot Wheels is one of the most famous die-cast toy cars series available and was introduced by an American toymaker in 1964. Since then, Hot Wheels cars have become toys that any child will love! This pajama-top features the Hot Wheels car known as the Bone Shaker with the phrase ""Challenge Accepted."" The pants feature an all-over print of different Hot Wheels cars and the Hot Wheels logo. The pajama pants contain an elastic waistband that fits every fan, and the whole pajama set is 100% polyester. These are the best!