you are buttfucking her (or him) and when you take you penis out it has shit on it and you make multiple shit streaks on her (or his) back, ass, or chest some longer streaks than others, making it look like buildings in a city. after that, to make it a "Christmas" in dirty Manhattan you cum all over the shit
Thad: Yo Chad, wanna come over we’re have a dirty Christmas tree Chad: no way, is it going to be with Tina? I heard she got Christmas treed last year
Thad: ya bro make sure you drink lots of water, we need you cumming buckets bro