After I earned eight badges I went to check if there is something interesting in all the buildings in Lumiose City. In one of the buildings on the Northern Boulevard (without a name), I went to the 2nd floor, and something really creepy happened.
The music stopped. The screen faded a few times. I was unable to move or do any actions. Then a Hex Maniac girl floated around me in absolute silence. She floated away at the end of scene, saying only...

I went around searching for the girl or any clue. I found nothing. It was a regular cubicle-office floor without people. 1st and 3rd floors have people doing their own stuff.
Is this some kind of developer joke, easter egg connected with Pokemon creepypasta, or is it something else?
Album of images of the above-mentioned events. (Original Source: Reddit /r/pokemon post, "GameFreak scared me once again...")
I experienced this. Check it out if you dare :)
13 Answers
I'm guessing it has something to do with either Rotom or Cresselia in X/Y (I'm playing X and I got the eerie-hex-maniac-girl-ghost too). The Strange House (at the base of Reversal Mountain) in Black2/White2 is where you get the Lunar Wing to catch Cresselia on Marvelous Bridge (also haunted), and in Diamond/Pearl, Rotom can be found in the haunted Old Chateau in Eterna Forest. I could be wrong of course, it's just a theory. There's still LOADS of stuff we don't know about X/Y yet. It might even have something to do with Darkrai, for all I know. Sorry I couldn't be of much help.
0Though I personally have not tried this, a forum post on Marriland (and brief Google search) says that you can
Bring Rotom to the floor on Tuesdays to obtain Rare Candy.
Other sources (none that are particularly reliable, note) say that it has to be at 9pm.
There is Youtube video about that now with all clues.
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