Borderlands 2 has a lot of outhouses—or porta potties, if you will—around every bandit camp. More than a couple of players seem to have stumbled upon overflowing ones, which you can see an example of in the video above.
For all I know, knowing Gearbox, this could very well be a feature and not a glitch.
Regardless, have you ever seen a death so horrific? First the Siren electrocutes the Bandit, and then suspends him in the air in a swirl of outhouse poop using her Phaselock action. That's a lot of stinky feces.