Dr. Simpson (her first name has never been revealed) is the chief of complicated surgeries at the invasive care clinic. Homer is devastated when he can't find any successful Simpson men to prove to Lisa that there is no genetic condition causing intelligence deterioration. As a last-ditch effort, he grabs Dr. Simpson, who explains that the defective Simpson Gene is only on the Y (male) Chromosome. Dr. Simpson looks a lot like Lisa, but older, and her hair is more down than up. Her position in the Simpson family tree is unknown.