Room signs
We put up a few signs on the night of the party. There were several signs at the entrances warning people about the indoor-only house elves.
The Azkaban video also had a short section about the (naked Sphynx cat) house elf:
The other signs helped give names to the themed rooms:
First, we retired the “house elf” video and pillowcase costume for the cat. Because there were people going in and out of the house to get across to Hagrid’s Hut, we decided it was best to just keep the cats locked upstairs.
Second, we found a wonderful metal Room of Requirement sign at the Harry Potter studio tour just outside of London during this year’s vacation. That’s been on the bathroom door since returning home — and fit in perfectly with the party.