Scariest of all were the games that everyone seemed to know, even without the benefit of YouTube tutorials -- tricks that supposedly unlocked magical powers or malicious spirits. And the funny thing is, these games have been going on for generations because on some level, they work.

For many of us, gathering with a group of unsupervised peers and scaring the shit out of ourselves was a rite of passage. At slumber parties we watched horror movies, told ghost stories and strapped ourselves to railroad tracks while high on cough syrup.

6 Bloody Mary

For the holy grail of pants-shittingly horrifying party tricks, look no further than Bloody Mary. The game goes like this: You stand in front of a mirror, alone, in the dark, and say "BLOODY MARY BLOODY MARY BLOODY MARY!" And then (allegedly) a woman appears in the mirror. Then she scratches your face off.

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If it's real, it really shouldn't be legal.

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"You'll be hearing from my lawyer, Mary."

But after weeks of searching through archived newspapers and microfiche, we haven't actually found anyone who summoned a psychotic person via mirror. Still, at this very moment, somewhere there's a 12-year-old kid standing in a bathroom whispering "Bloody Mary" loud enough for her giggly slumber party guests to hear her. Do you know why?

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Because she's going to see something in the mirror.

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Even if it's just the realization that all her best years are behind her.

The Science:

If you stare at a mirror long enough, you're going to see some freaky shit.

One psychologist set up an experiment where he had 50 people gaze at a dimly lit mirror for 10 minutes. Afterward, participants wrote down what they saw, if anything. Before we share the results, bear in mind that this was not a slumber party and no one was told they'd see anything horrific beforehand.