An expression way to common than it needs to be. It is used by scrubs who think they're funny and cool. The manner in which the scrubs use it is supposed to mean "Your ugly and I'm better than you!" but instead has the reverse effect.
the prank in which one person tricks another by suggesting that if one's hand is bigger than their face, they have cancer. But upon placing their hand over their face, to test themselves out, the prankster smacks the person's hand into their own face.