I thought maybe starkers might enlighten us. He knows about those sort of things.
I'd like to be able to enlighten you all, but I was at home at the time, scoffing down a bowl of curried cabbage while watching my protoge, Mr Methane, on TV. I did, however, peel off a ripe one later that evening, which may or may not have been responsible for the pungent whiff in the air that night... but I doubt the dark greenish/brownish goo was mine.
After a rather unfortunate accident some years ago that ruined my best pair of blue suede shoes - not to mention my best pair of flared leather pants because is was more than ankle deep - I ensure all the water is drained off the boiled cabbage to ensure absolutely dry farts. So if there was a greenish brown goo that night, I'd say there is somebody going around impersonating me... somebody who may have learned the secret of curried cabbabge.... but not how to control their sphincter.