Ault animation is animation that is targeted at adults. For western audiences, the primary reason for a program to be described as "adult animation" is adult humor. Popular programs such as FOX's The Simpsons and Family Guy contain humor that some parents might find unsuitable for children. However, adult humor can be innocuous as well, and simply above an average child's ability to appreciate, as is the case in many early theatrical cartoon series, such as Looney Tunes and Popeye, as well as in many modern TV cartoon series, such as Animaniacs, The Powerpuff Girls and SpongeBob SquarePants. These cartoons will often contain slapstick comedy for children, but also jokes which can be appreciated only by older audiences, such as pop-culture references, political satire and sexual innuendos. Some animated series, such as Max Fleischer's Betty Boop cartoons of the 1930s and Nickelodeon's Ren and Stimpy series, walk the line between both types of adult humor.