Lyric discussion by JeffKaos71 

Cover art for Pencil Rain lyrics by They Might Be Giants

the first line (The possible dream) is a reference to "The Man of La Mancha - Don Quixote" The Impossible Dream)

'They Might Be Giants' (the bands name) refers to a quote from Don Quixote when he sees windmills but he thinks that "They Might Be Giants" and he tilts them. It is actually a movie from 1971 of the same name (They migth Be Giants) about Sherlock Holmes in modern day Manhattan that has a reference in it to Don Quixote in it.