The rabbit has taken to pooping on the couch. Fortunately it's very easy to clean up since his scat is hard and dry as beads, but it's still unpleasant. The internet tells me Pipkin is probably marking the couch as his territory (high ground is desirable). Hopefully neutering him will help...
In the mean time, I have to become an expert at rabbit posture. A subtle change to the curve of his back and the height of his butt indicates that it's time to shoo him off the couch. He hops off indignantly, leaving one or two little brown balls in his wake (or a dozen of them if I wasn't fast enough).
I hope O.'s parents don't find out about the defilement of our couch for a while. We always put a clean sheet on the couch before they come over, so it really shouldn't matter, but it might freak them out anyway since the standard of clean/unclean that they gravitate toward exceeds even levitical standards.
Pipkin, you need to learn to share. Everything in the house can't be yours!