In the sprawling, yellow-skinned universe of The Simpsons , most antagonists are driven by petty greed, laziness, or simple malice. But Sideshow Bob (voiced with Shakespearean relish by Kelsey Grammer) is different. He is the cultured, vengeful, and unhinged foil to Bart Simpson—a man whose genius is matched only by his homicidal obsession with a ten-year-old boy.