Shamelessly stealing an idea from Gil, here's a last-minute riddle for Passover. I heard it from someone who heard it from an academic (whose name I forget) who lectured about the history of the Passover Haggadah. (If anyone else heard the lecture, please let me know who it was so I can credit him.)
The question: Of today's standard (Orthodox) text of the Haggadah, what part was added most recently? When and why?
My own followup question: What other part of the Hagaddah should have been changed for the same reason, but wasn't?