mole at the counter
A turtle's head. A turd that needs to come out.
"Elementary, my dear Watson. From these footprints, I deduce that our quarry was a left-handed doctor of unusually short stature, who had known prosperity but had recently fallen upon hard times, and judging by the short, irregular length of his stride it is apparent that he had a mole at the counter."
mole at the counter
Precisely the same as turtle's head. To be in need of an imminent dump.
I'd love to stay and chat, but I've got a mole at the counter and he isn;t going to wait!