Grover helps Ernie sing a song about opposites. His task is to demonstrate the opposite of everything that Ernie does. Unfortunately for Grover, he gets the more difficult part of the song.
Mah Nah Mah Nah sings a song about words that are opposites. He uses visual indicators to describe each word, making it easier to understand how two words are opposites.
At dinner, Bart expresses his excitement about Homer becoming an astronaut and asks for the opposite of the word, "shame," to accurately represent his feelings. Marge lists the wide range of emotions she experienced when she learned about Homer's venture into outer space, and several of the words she uses are synonyms.