We are the music-makers, and we are the dreamers of dreams.
You can get that image as a t-shirt. It seems that most people know that quote as Willy Wonka, from the 1971 film adaptation with Gene Wilder.
Through a turn of fate, I never saw the film as a kid. I only discovered it when I was a teenager, the year I was taking English Literature, and I noticed that a lot of Wonka's poetic asides are allusions. Via Christina Wodke, I learn that Thomas M. Brodhead tells us that this did not come from Roald Dahl, but from a script doctor who wrote the screenplay.
When Quaker Oats (yes, the Quaker Oats company!) decided to adapt Roald Dahl's Charlie and the Chocolate Factory for film, Roald Dahl was asked to write the screenplay. Dahl produced a fairly literal translation of his book that was deemed unacceptable by the studio executives. The young writer and script doctor David Seltzer was then asked to “improve” Dahl's script. The result was a recalibration of Dahl's story with many significant changes (e.g. rival chocolatier Slugworth became a central character in the film as a tempter of the children, etc.) More importantly, Wonka was cast in a darker light, with an ambiguous stance toward the children (as opposed to the sprightly and somewhat avuncular candyman of Dahl's conception.)
In the finished script, Wonka's dialogue is peppered with literary quotations and allusions not found in Dahl's book. They were all introduced by David Seltzer as part of his rewrite of Dahl's screenplay.
Brodhead has tracked down sources for the allusions (including Arthur O'Shaughnessy's Ode, which gives us “we are the music makers”).