Stuck, are we?
Z is for Zippity Doo Dah, which the Trasks went off to a private room and sang, right after proposing to Judith, getting Quentin One arrested, walling up Barnabas, etc.. I picture them dancing and flailing their limbs in a spazzy manner.
Next time around, if we run out of Z DS references, I want to use Zardoz. I just like thinking about that giant floating head. Plus it's fun to say. Try it.