Eartha Kitt recorded her lines shortly before her death in 2008, more than a year before the episode aired.
Eartha Kitt & Anne Hathaway have both played Catwoman. Kitt in Batman (1966) & Hathaway in The Dark Knight Rises (2012)
This was the 450th episode.
When Princess Penelope first appears on screen Lisa is reading Angelica Button and the Infinite Armoire by T.R Francis. The Harry Potter parody first appeared in The Haw-Hawed Couple (2006)