"Pull in and out of his ass?" That makes no sense. You can't pull in someones ass. Well, you CAN, but thats a totally different context (which I'd like to see the video of).
Edit: If I did I would show them I swear. How about this--------- If I ever purchase any said tits, I'll show em, okay? And for now I can just keep stopping by.
Okay, now, to be fair...as Necuratul worded it, the "shit" refers to an event, not an object, such as a penis.
Let's look at Eric T's post. "His dick out of your ass?" Here, the "shit" is referred to as "dick" (an object, not an event) and "behind my back" is referred to as "ass." So we have "Pull his dick out of your ass?"
With Susperia's addition, we have "His dick in and out of your ass?" - With that addition she has completely changed the meaning of "shit" to the entire act of anal sex, which is an event. The word "Pull" does not necessarily need to be added, since now we know that the shit he was trying to pull behind his back was the event of anal sex.