Before you say I'm insane, remember that I have overactive imagination (even though I'm 99% sure my mom made that up).
Every time I get up in the night I hesitate for a while, then get up, and on my way down stairs I will always see a face or something for a split second, then disappears. Most of the time they don't really scare me because I know they aren't real. But sometimes, after reading something creepy I would see if and be scared stuffless. I can't really control this unless my mind is completely blank.
Tl;dr LSD gremlines are trying to get it on with my cortex and gives me bad trips.
Fun fact: The face kind of looks like slenderman.