Okay, although it is "Goo Goo G'Joob" officially in the lyric (I remember it being printed on a lyric sheet of a greatest hits LP I owned), the classic literature source may be apocryphal:
Some sources have suggested that the phrase "goo goo g'joob" is from Finnegans Wake by James Joyce. According to the "Paul is dead" rumor, "goo goo g'joob" are the last words uttered by Humpty Dumpty before his fall—a fall that cracked open his head, much like Paul's rumored fatal car accident. According to Allen B. Ruch, however, Joyce did not use the phrase "goo goo g'joob". In his website "The Brazen Head", Ruch cites the phrase "googoo goosth" as the closest Joyce gets to "goo goo g'joob" in Finnegans Wake.