It's consistent with a current real world holiday, and I have yet to find anyone who showed up to any kind of different circumstance, so it was already like this when everyone got here. It's normal for our thoughts and state of mind to affect the Dream Sphere, but what's happening is a lot more specific, showing everyone their desires, than what is usually seen. I'll need to cross reference locations with high Dream Sphere activity and especially deeply held holiday traditions to see if anything else like this might have happened before.