In 1970, Parker Brothers introduced the world's first indoor ball with its original "non-expanding recreational foam" material, or NERF. The NERF ball was an instant success, with 4 million sold by the end of the year, meaning kids across the country were able to break their parents' most sacred rule: "No playing ball in the house." After the quick success, Parker Brothers quickly released the NERF Super Ball and the Nerfoop (an indoor basketball hoop) in 1972. But it was the NERF football that would go on to outperform its real counterpart, becoming one of the best-selling toys of the 1970s.