I know this is an old and juvenile joke, but a bunch of us at the Brooklyn Meeting retreat this weekend up at Powell House got a kick out of this "Kitty Litter Cake" made the resident chef Kris.
It's basically a chocolate pudding cake, with crumbled up cookies on top to look like the litter. The "poo droppings" are just shaped Tootsie Rolls. I think dying some of the cookie crumbs green would really add to the versimillitude of the whole thing. But Kris's version got a lot of reaction from kids and adults alike.
Ooo, gross! Mmmm, delicious.