Totally Spies! (2002)

Season 3: Episode 21

A villain who wants to be the most evolved and advanced person on the face of the planet invents a crazy device which physically shrinks peoples' brains, causing them to regress to a more primitive state. Essentially, he's turning everyone into cave men. As society becomes more primitive, the world (including Beverly Hills), begins to turn into a lawless Mad Max-type society. In a b-story, Sam takes ""charm"" lessons to impress an extremely cultured boy at school.