"The notion that animation is just for children has been consistently debunked, as R-Rated animated films have always served as a legitimate form of artistic expression. While the popularity of Dreamworks Animation, Pixar, and Illumination may have shown that animated family films can be very lucrative, there's also a desire to tell more complex stories within the medium that are aimed at a mature audience. Given how popular adult animated shows like 'South Park', 'Family Guy', and 'BoJack Horseman' are, it's a bit surprising that there aren't more R-Rated animated films consistently released on the big screen. Animation is a medium, not a genre, which means that the types of animated films that earn an R-rating from the MPAA can vary dramatically in terms of style, approach, and intent. Here are R-rated animated films that can be called masterpieces, ranked." - collider.com
