When Maggie does better than Lisa on an IQ test, Lisa becomes so despondent over no longer being the smart one that she tries to change her identity.
Always Someone Better: Maggie to Lisa. Later subverted when it turns out Maggie only appeared smarter because of clues and hints Lisa was giving her. Double subverted when Maggie starts playing the saxophone.
Marge: All of my children are smart. Some are just smarter than the others.
Bart smiles ominously and puts his hand on Lisa's shoulder.
Bart: Welcome to the others!
Disappointed In You: Marge and Homer when they see Lisa trying to sabotage Maggie's mental development. Homer in particular says this by playing with the Phonic Frog toy.