Arthur and D.W. make fun of each other with different insulting nicknames. After Arthur calls by her full first name, Dora Winifred, D.W. has a nightmare and learns that calling people names can hurt them. Arthur, Binky, and Brain find a key in the grass while looking for a baseball they lost. Arthur theorizes that it is the key to the city, Binky hopes it belongs to a sports car, and Brain thinks that it opens an upcoming science museum. They argue over who gets to keep the key, despite none of them knowing what it unlocks. It is later revealed to open the sprinkler control system for the school's baseball field.