Silvermask

Silvermasking is a fraternity sex game played on girls by frat guys. One frat brother begins having sex with a girl in private. In the middle of intercourse, other frat brothers burst into the room wearing nothing but masks made of tinfoil and tinfoil covering their genitals. The silvermasked frat brothers dance around the copulating couple, typically having the effect of seriously freaking out the girl. The reaction of the frat brother who is engaged in intercourse could range from embarrassment, to anger, to unabashed hilarity -- mostly depending on whether he was expecting the prank or not. Silvermasking is purported to have been a common prank (maybe invented?) at the SAE fraternity at the University of Illinois in the mid-1990's.