In the United States, before the enforcement of the Hays Code, some cartoon shorts contained humor that was aimed at adult audience members rather than children. Following the introduction of the Motion Picture Association of America film rating system, independent animation producers attempted to establish an alternative to mainstream animation. Initially, few animation studios in the United States attempted to produce animation for adult audiences, but later examples of animation produced for adults would gain mainstream attention and success. Adult animation in the United States includes shows with superhero, sci-fi, and fantasy elements. Some of the most prominent animations with these mature themes include The Simpsons, Bojack Horseman, Futurama, and Archer, along with other adult ani