My friends and I were talking about picking up girls at the bar, and we started talking about a guy we always meet at the bars, and how he almost picked up a fat one.
Anyways, they were talking about what they told him to do and we came up with some that he should have said. So this was a couple weeks later and we were reminiscing about the blessed event, and were coming up with funny things he could have said.
We got to a point where we were talking about shitting.
One of the pickup lines was,
Him: Hey, you're looking good tonight
Her: Thanks.
Him: Wanna get out of here and shit on me real quick?
Another variation was
Him: Look, you know it, I know it, it's either me or no one, wanna take a shit on me real quick?
And that's how the line "Wanna shit on me real quick?" became a meme for me and my friends.
It's hilarious if used correctly, but if you use it at the wrong time it just kills the mood.