Totally Spies!

Head Shrinker Much? (3x23)

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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.