Today’s XKCD — wow! I remember us little girl friends in elementary school (while living in Guam), daring each other to do this when we hung out in each other’s houses! (Not the two mirror thing, though — just the one.)
FREAKED ME OUT so much that I never stuck around in the dark bathroom to see if it worked.
I still get mildly shiver-y when I’m in a dark bathroom because of that! Ah, the irrational mind-tortures we would do to each other when we were children….