Young or old, if you enjoy cartoons and animation, then you'll enjoy Kids Next Door. The show's concept is relatively simple: a secret agency composed of ten year-olds fights evil adults; the result is a imaginative world that is both inspired by several genres and movies and creates a distinct universe. The comedy is wide-ranging in the ages it appeals to, the action is entertaining despite the show not being the pinnacle of animation, and the plots are original while paying homage to it's sources: many of the episodes are homages with a KND spin that works extremely well. The characters that make up this rich universes might seem like stereotypes at first, but they grow into completely three-dimensional beings that can be both fun and poignant.
Hands down, KND is one of the best original shows on Cartoon Network, keeping with the explosion of comic creativity in the channel that is leagues ahead of most other kid-oriented channels (Nick and Disney come to mind).
