Like many of you, I loved the movie “Once” which introduced me to the music of Glen Hansard. NPR recently broadcast a concert of Hansard and his co-star and now girlfriend Marketa Iglova on their "Live from the Artists' Den" series and I happened to catch the last half including what I gather is a regular routine where they insert a segment of  “Pure Imagination” from "Willy Wonka" into their song “Star Star”!  
Unfortunately I couldn’t find that clip but my YouTube search did come up with this tribute performance by 7 year old Ethan as well as the Gene Wilder original and a visually shaky but audio clear Hansard concert clip from littlexwingx07.  At 1:40 into the clip you will hear them break into “Pure Imagination”.