Nothing?
That's so funny...because I just pooped.
I felt it come out. This place smells like poop. I feel devoid of poop. Most of my senses are in agreement as to the event of poop being evacuated.
...and yet...
IT'S A GHOST!
Yes, a delightful little [read: enormous] poop banished to the bottom of the pipe. Ashamed, even, perhaps. Now this is cause for celebration! Fuck American holidays, I just pooped out magic invisible poop!
Eastern Block Tourist: You mean dat ven you make poop, you cannot see poop?
VAT A COUNTRY!!!