I love this comic, but I swear I've read pretty much the exact same joke but with different things other than poop and such. Maybe it's just deja vu or something... It feels like maybe a Far Side or a Perry Bible Fellowship... or maybe Boy On A Stick and Slither... Gah, it's driving me nuts! Or I could just be imagining it.
Now, of course, I'm not trying to knock the work, and I think this is probably my favorite Sunday Funnies comic, but it's just eating away at my mind that I've seen this punchline before! Ah well. I'll either remember it or not.