A lot of sitcoms feature smart children in the cast, but they're usually not that smart. Alex Dunphy (Ariel Winter) from "Modern Family" gets high grades, sure, but she's not skipping multiple school years or, like one kid on this list, successfully taking over the world. For most sitcoms, the child characters aren't smart so much as they are precocious. This approach can be amusing — See: Manny Delgado, also from "Modern Family," – but, more often than not, they can grate on the viewer. These five sitcom child genius characters are not just gifted: They're genuine prodigies.