Dexter is tired of Dee Dee's bad singing, so he tries to "improve" her singing by transforming her voice to a beautiful one, but ends up giving her a baritone voice, which is even more annoying.

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Past the vaulted doors lives the smartest boy the world has ever seen, Dexter, boy genius! He's constantly creating dazzling, worldsaving inventions in his secret laboratory. His big sister Dee Dee frequently wrecks his experiments. However, he has bigger problems such as his nemesis, Mandark, his brilliant rival at Huber Elementary School. Mom and Dad, of course, have no idea what their little angel is up to.