A legitimate game exists where the goal is to have sex with the people around you. No, this is not one of the many drinking games you played in college, it's an actual game called Clusterfuck.
The not-so-innocent game was created by Cards Against Humanity, Doug WIlson and Zach Gage, and it's pretty straight to the point. The quickest way to win is to have a threesome, just like in real life. It's good, filthy holiday fun that gives people an excuse to hook up.
It's all in jest, of course, but shit could get real if liquor is added to the equation.